The DS was supported ~2 years into the 3DS lifespan with 1st party games (Pokémon Black/ White 2 in late 2012) despite 3DS being backwards compatible. The Switch Up won't release before may- july 2025 as it seems now, so a bit less than 2 years of first party (cross gen) support is just logical. The Switch won't sell less than 4 million next year and at least another million till march 2027. They will have a userbase of 155- 160 million units, maybe even the best selling gamin system of all time. Nintendo can't and won't ignore that. 

@killer7 The problem with comparing the DS/3DS transition to the Switch/Switch 2 transition is that the 3DS was a much less successful system than the DS. As a result, it made sense for GF to prioritize the DS more than the 3DS. They jumped ship from 3DS to Switch pretty quickly because the Switch proved early on to be a huge success. They even seemed eager to jump off the GBA and get to the DS quickly (FRLG & Emerald launched less than a year apart and DP was originally slated for 2005).

Obviously we don't know for sure what will happen with the Switch/Switch 2 transition, but while I feel like Switch 2 will sell less than Switch 1, I still see it being a raging success. As a result, I can't see there being any major titles for Switch released after 2025. Just some remakes, ports, remasters, etc. (and even that would probably end by the 10th anniversary of Switch). I don't expect Switch 1 to sell a lot after Switch 2 releases (maybe somewhere close to 5 million).

Agreed I'd like to see it be only next gen. In general I think when people speculate about Nintendo starting to do lots of cross gen games like the other systems do I think that is not going to happen. They've never done that other than the two times they've had Zelda games coming out so late that they just released it cross gen at the new system launch. I'm just saying I could see them wanting to take advantage of the Switch's user base to sell one more pokemon game on it, but only if they are sticking with the 3 year cycle and gen 10 is coming out like 6 months after Switch 2 launches. And I believe there was a pokemon game that came out on 3DS after the Switch launched, so that's kinda what I'm basing my idea of its possible they'll also release it on the older system.

And yeah with another Legends game coming out next year, it'd be absurd if they once again did a Legends plus mainline gen game coming out in the same year. Definitely don't want to see next pokemon gen before holiday 2026. I bought Sword as my first pokemon game since Red 20 years earlier and was pretty disappointed at how mediocre Sword was compared with how cool I remember playing through Red was. I also got Legends Arceus which definitely seemed cooler but I still haven't played that far into it so I can't say for sure. All anyone wants Game Freak to do is allow themselves the development time to make an outstanding pokemon game and continue the evolvement of the series that Arceus and SV started.

I think the problem if you will to have crossgen releases between Switch-Switch 2 is that the Switch is so weak that it would really constrain the type of games made for Switch 2 if they have to be playable on Switch as well. Its not like PS4-PS5 because the PS4 was still capable of running games like Horizon and God of War on a pretty decent level. So gen 10 being cross release on Switch means that gen 10 would be exactly on the same level as Scarlet and Violet, not exactly optimal.

@Slownenberg If they stuck with the three year cycle, then maybe it could be next gen. At this point though, I feel like Z-A will be the holiday 2025 title for Switch, so definitely no Gen 10 in 2025. 3DS had a Pokemon game the year the Switch launched, but that was basically the third version for SM. Not a new generation.

The 3DS got first party games 2 years into the Switch's lifespan! Metroid: Samus Returns, Hey Pikmin, Ever Oasis, Pokémon... just to name a few. The 3DS sold around 5- 7 million units in the Switch's launch year (basically flat to the previous 2 years before). "Jumping ship pretty quickly" is not the act i would call that. The PS4 got Horizon, GT7 and GOW as cross gen titles and that was it with first party. The 3DS got more than 3 titles, and it where exclusives wich where not availible on the Switch. We do not know how sucessfull the Switch Up will be but it's not likley that it repeats its predecessor's sucess. If it flops, i see around 30 million minimum. If its sucessfull, 100 million minimum- 120 million maximum. No way its gonna repeat the Switch's sucess. Maybe we see a surprise but i don't think so. Yes the Switch was not backwards compatible and dirty cheap compared to the Switch, but the Lite will go down to ~150$ max. eventually and this pricegap won't be small as well.

@killer7 I was referring to Game Freak specifically and not Nintendo as a whole. They released USUM the year the Switch launched and then their next game was LGPE on Switch. It actually marked the first time that, for Nintendo systems with core series games, the first core series game on that system wasn't a generation starter.

I do expect Nintendo themselves to release titles on Switch, mostly remakes, ports and remasters probably through 2027.