It was arguably announced due to the so-called backlash of the Pokémon Direct. Regardless though, saying that a core RPG Pokémon game is being developed alone can cause big waves. You're talking about the second best-selling franchise in the history of video games (behind Mario) and a system seller. And made by Game Freak, which is huge because they develop the mainline games while mostly leaving the spinoffs to external partners. It's like The Rock being announced for a guest appearance for RAW, people will get excited.

Killzone, Knack, MLB 14, LittleBigPlanet 3, Bloodborne, MLB 15, Ratcher and Clank, MLB 16, MLB 17, Uncharted The Lost Legacy, Knack 2 all took a few months from announcement to release. That's not counting the remasters and such like TLOU Reamster, Nathan Drake Collection, Heavy rain, Beyond Two Souls, God of War III, etc.

MS also has titles that released a few months after being announced like Ryse, Forza 5, Forza horizon 2, Forza 6, Forza Horizon 3, Rare Replay, Forza 7, Super Lucky's Tale.

It tends to happen more for the lauch window titles cause they're announced when the console is shown off or the E3 right after the console is shown off. Don't expect the same trend to continue beyond that, there will still be some game that announce so close to the announcements but not with the same regularity as they do at the beginning. 

They didnt show anything for those games, they just confirmed they are in development, most likely they want propore revile with trailer and they will give year of release. But that doenst mean they will not be relased in 2018. esapcily that said Switch Pokemon will need more than a year, holiday 2018. is almost 1.5 year from E3 2017. Yoshi and Kirby had full trailer and year of release and they will almost certain be released in 1st half of 2018. (before E3 2018.).

Thats point, E3 that's focused on 2017. games did not stopped them to show some 2018. games even to announce some games that will be released maybe beyond 2018.

I was right, focus was on 2017. games with few announcement of games that will be released outside 2017.

Its not point only about upset fans, but point that they wanted that after Pokemon 3DS announcement to be sure that Pokemon is in development for Switch, most likely we can't hear anything about that game until next year. Its similar story for Metroid Prime 4 ananucment, and actualy Regie talked about that, how Metroid Prime "is a franchise that we know people have been very eager to get some news". People were very pleased because they are getting 2D and 3DS Metroid, you can bet that people would be angry if there was Metroid 3D announcement with just remaster of 2D Metroid. E3 media measure numbers show that Metroid Prime 4 announcement one of biggest news of E3, Metroid Prime fans literally cried. :D

http://www.neogaf.com/forum/showthread.php?t=1392441

Nintendo done great job with E3, and nobody really question their E3, Pokemon and Metroid Prime 4 announcement are totally logical because reasons I mention. Again, fact is taht you dont know if those game are 2018. games or not, Nintendo didn't said anything about year of releases, only fact we have they said Switch Pokemon will need more than a year of development and holiday 2018. perfectly fits that info.

What Reigge said is really answer on lotsa things you dont understand or you dont want to understand:

“You know, for us, we believe that having hands-on opportunity married to an announcement is really the best way to do it,” Fils-Aime told IGN. “And so let’s take Super Mario Odyssey for example. We could have announced it months ago, but we weren’t yet ready, the team wasn’t ready, to show it and to let the consumer really understand visually how the hat mechanic works, how the capture mechanic comes into play. And so that’s how we think these through.”

“For certain games, games that will be in development for, let’s call it a decent amount of time, like Metroid Prime 4 -- also, given that it’s a franchise that we know people have been very eager to get some news -- that’s when, fine, we’ll share it. We’ll share it early,” Fils-Aime added. “Others, we want to hold closer in and reveal it when the gameplay is going to be available. It literally is game by game, title by title, how we make that decision.”

http://adria.ign.com/metroid-prime-4/15729/news/najava-za-metroid-4-je-dosla-prerano-reggie-nam-je-rekao-zas

My biggest issue with Nintendo, is that if the series isn't Pokemon, Mario, Zelda, or Kirby -there's no guarantee there'll be an entry for 5-10yrs

It's about both, you can't make a couple really good games and then sit on your laurels, and you can't just make a lot of terrible games and say "oh well atleast we tried". You need a steady stream of quality titles to have a successful console that people will buy and remember fondly.

So your concern is that they have just 4 system sellers in the first 8 months after launch? 

Absolutely correct. Kind of like how SIE didn't rest on their laurels when they created MLB the Show 07. They went right on with The Show 08 and the Show 09.

I remember falling out of my chair, giddy with anticipation, when they ran that trailer for MLB the Show 10.

That's how Sports titles work...They get a new entry every year. MLB The Show is also arguably the best sports games out there.

It's amazing how they manage to make them so fast, while Nintendo will take years to make a Mario Kart and then port the same one over to their next console cause making a new game would be too much work and resources, and they'd rather keep that money in the bank so their fans can brag about how much money their favorite corporation has in the bank like they get a cut from it.

Is that a bad thing? New installments for certain games are fine releasing every couple of years, as some of them like Mario Kart have great replay value. Games that do yearly releases give me burn out, actually.

rofl