I'm kinda in the minority that really hopes the next generation games are on the Switch, but moreso for technical reasons more than anything else. I want to see the main Pokemon series games' graphics develop even further. Maybe we'll get a Pokemon game that'll be compatible with VR, wouldn't that be cool? I doubt the Switch is compatible with VR, but y'know, just kind of in a hypothetical situation, it's really not good to keep limiting Pokemon games to one system all the time.
I feel conflicted because the DS family has been in existence for more than a decade and each one eventually gets retired in favour of another platform. The original DS, the DSi, the DSi XL, the DS Lite, there's so many iterations of the Nintendo DS family that are so similar to another that personally, I don't see anything wrong with a breath of fresh air and going with the Switch as the new "handheld" platform of choice for Pokemon games. It's knocking out two birds with one stone--you have the opportunity to play Pokemon on the big screen and take it with you if necessary--thus kind of defeating the point of having a separate handheld, except if you're really that picky about portability.