Well its seems those games are remastered not simple port, more like MK8.5, Splatoon 1.5 and Smash Bros 4.5, probably they will have improved graphics (1080p with AA!?) and new content. Maybe you will get some discount if you have digital some of those games on Wii U. They don't take anything on Wii U owners (lol), you are not forced to buy those games on Switch. Also you need to understand that this generation ports/remasters are basically normal thing. 

And I already wrote why thats good for you like Switch owner, "its good for platform because platform will be more popular and more appealing for people who didn't had Wii U (I constantly seeing people who didnt had Wii U and planning to buy Switch saying they hope for more Wii U ports/remasters on Switch), and popular and successful platform means better sales and better sales means better support with more games".

Releasing two Smash, MK or Splatoon games in same time, even in same year (I would say even i same generation) doesn't make any sense.

I dont care whats good for the Switch. I care about whats good for Nintendo fans who still stick with them.

and why doesnt it make any sense to release ports of WiiU games and new games in the franchise around the same time?

Arent people who didnt own a WiiU dying to play these games on the Switch? No, everyone would rather have new games in the franchises than buying 3 year old games. It wouldnt make sense to Nintendo because they would get those sweet extra money from their fans. They should fucking give away these ports to anyone kind enough to still support their new console after the WiiU.

But if its good for Switch its good for Nintendo fans also, they will have better support and more games on Switch.

Beacuse games like MK, Smash Bros and now Splatoon are multiplayer online games that are meant to be play very long and whole generation, and thats why they are relasing one game per generation per console (actually probably only Nintendo IP/franchises that we have only one game per generation per console), so having two Smash Bros, or two Smash Bros or two Splatoon games in same year doesnt make sens at all.

Actualy you have lota poeple knowing that MK8, Splatoon and Smash Bros are great game but they didnt buyed Wii U from difrent reasons (but most obvous is beacsue its dead platform), and now they planing to buy Switch and they also want ports of those games on Switch. Also all those games will be most likely be available in 1st year of Switch, while Wii U got MK and Smash in second year and Splatoon in 3rd year. You can bet those game will be very popular and they will have great sales on Switch also, same like The Last Of US and Uncharted Trilogy have great sales on PS4.

Give them away with every Switch sold. THAT would be great for gamers. Every console comes with Smash 4, Mario Kart 8 and Splatoon Remastered. Every Switch owner will have the chance to play them and it could lead to new fans of those franchises. Its a win for gamers and it makes Nintendo look good. Win Win.

I can definatly see they bundle Switch with one port (maybe downloadable code so you can choose what game you want from those 3, like MK8 promotion on launch), but bundling 3 rematers/ports with Switch at launch isnt realistic at all (at least on Switch on launch) beacuse they know they will sale those games great in any case even whitout bundles. Also its sure they will not be all available at launch, probably only one will be at launch, they probably don't want to have multiple ports/remasters on launch instead of new games.