Ask yourself a few questions. Does Nintendo intend to release another game in the series on Switch? If no, then they'll port the game to Switch to make easy money and get a bit more out of their investment that they didn't get from Wii U. If yes, would having this game on the Switch help create hype for the next title in the series or make any future titles in the series obsolete? If it'll hype the series, then they'll port it in some form or fashion, be it a straight port, enhanced port, HD remake, collection, or otherwise. If it'll obsolete any further titles for the series on that system, they won't.
Using this method, we can explain/predict every port or lack thereof from Wii U to Switch. Mario Kart 8 Deluxe? It kind of obsoletes the series for Switch, but it doesn't seem like they intended to make Mario Kart 9 for the Switch, presumably because they felt like they didn't get nearly as much out of Mario Kart 8 as they could have. Splatoon? They didn't port it because Splatoon 2 was coming soon, and since they're fairly similar, having the first game on the same system right before the second released would definitely hurt sales, and make people feel like Splatoon 2 was a waste. Pokken? I really don't think that game is getting a sequel anytime soon. Maybe on a later Nintendo system. They may as well cash out with a port for the few fans it had and those who may have missed it. Captain Toad? They probably won't make another game, so they might as well. Even if there was another Captain Toad on Switch, having the first on the system exposes it to a wider audience. Hyrule Warriors? They definitely won't make another one of these anytime soon, and the Warriors series is just made for Definitive Edition style games. Bayonetta 1+2? Well 3 is coming out, and the first two didn't get nearly the attention they deserved, and Bayonetta fans need something to tide them over. Donkey Kong? Maybe they'll make another one, but if they don't, TF gets a bit more much deserved attention, and if they do, DK will be a little fresher in people's minds this way. Smash? We got a new game instead of a port because a port would have made the series obsolete for the rest of Switch's lifetime. You don't need two Smash games on the same system. Based on the sales explosion Ultimate has seen, I think they made the right call. They got a good 13-14 million from Smash 4, they don't need to rerelease it, we're much better off with Ultimate. NSMBUD? A lot of people were disappointed because they saw this as a sign that Nintendo didn't want to make another 2D Mario for Switch and wanted to just cash in a bit more with the Wii U's games. I think it was a last hurrah for the NSMB series before they reboot 2D Mario again. Time will tell. Yoshi's Wooly World isn't getting a port because the first game did pretty in line with what Yoshi games usually do and Crafted World is coming out soon and is the same game with a different aesthetic. Mario Tennis got a new installment instead of a port because Ultra Smash was garbage and would have just hurt Mario Tennis Aces by proximity. Nintendo wants us to forget that one. Kirby and the Rainbow Curse did horrible and didn't seem to have much interest in it even for a Wii U game, so Nintendo decided to go back to classic Kirby with Star Allies and have people forget Rainbow Curse too. Same with Mario Party 10, Nintendo saw it wasn't working and didn't want to push it any further, deciding to go back to how Mario Party used to be. Some titles, like Wii Party U, Wii Fit U, Wii Sports Club, and Nintendo Land, were tied specifically to the Wii U and likely will get spiritual sequels at some point instead of ports, like 1-2-Switch is for NL. You could do this for every game on Switch with a corresponding Wii U title. So with that said:
Super Mario 3D World: Probably. Captain Toad showed the gamepad isn't an obstacle for porting, so why not port this, maybe even alongside 3D Land? I mean, unless it's like those games that Nintendo wants us to forget, but it did well and was pretty well liked, so I doubt that.
Xenoblade Chronicles X: Absolutely. Yes, we've had XBC2, but XBCX is a spinoff, so they don't get in each other's way. So how could they not give it another chance? As I said with 3D World, the gamepad probably isn't an obstacle that clever design couldn't get around. This game deserves it, and I think Nintendo knows there's money to be made here.
Super Mario Maker: Absolutely not. No way they port this. We're getting Super Mario Maker 2 at some point, or they'd have already ported this for a 2018 release to pad the horrible software gaps we had. Porting this would definitely hurt SMM2, just think of how the different online communities would cannibalize each other. If this gets ported, SMM2 is coming for the Switch successor, but I highly doubt that will happen. SMM2 might very well be the surprise title Nintendo was teasing that would "make fans happy" or whatever vague thing they said. Could also be the online title they teased. So we might even be getting it this year.
Zelda Ports: Probably at some point yes, but I doubt they'll be straight ports. They'll likely be combined into a collection, perhaps with bonus content or even a whole new HD remake! Depends on what Nintendo wants to invest into them. They sold alright for remakes, so a little more investment in more features/an HD Skyward Sword would make sense, but then they may want to sell Skyward Sword HD standalone, in which case they may not port them so as not to flood the market with Zelda ports.
Pikmin 3: Depends when Pikmin 4 is coming. It seems like it's been struggling, but it might be out this year for all we know. If Pikmin 4 is a 2020 or later release, expect Pikmin 3 to come to Switch to hold us over until 4. We might even get lucky and get an HD collection of the first three games! (I can dream...)
Other: There are a few others I see happening. First, with the same logic as Pikmin 3, Metroid Prime Trilogy is likely to come to Switch. A Wii game I know, but worth mentioning. Paper Mario will get ported only if Nintendo continues with its current path with Paper Mario, and only if there isn't a new one well in development already, which seems possible since Color Splash released close to the end of Wii U's life. Wonderful 101 and Tokyo Mirage Sessions #FE seem very likely if Platinum and Atlus are up for it, which they probably are. The only other title I can think of worth mentioning with any chance of a port is Pushmo, which I could see being released as a collection in the future as a digital only release.