Great points! This is an unusual situation. My impression has been that Nintendo usually has several games near completed or fully completed well on advance of their release. What we don't know is how long Nintendo expected or anticipated a Switch 2 delay vs. when the news broke.
The Wii U situation with limited games in the holiday season for 2016 is the comparison folks may go to but to me they're so different because that was an especially unsuccessful system. And then I suppose I have to also consider 3DS being sunset that year with significant first party releases locked to that system, including Picross 3D, Mario Party, Pokémon Sun/Moon and SMM 3DS. Even when Wii was poorly supported towards the end of its lifespan we got a major holiday game in Skyward Sword.
I guess my hope or optimism here is that Nintendo has known about the delay much longer than when it leaked, and regardless has had a plan B and so on. I'm just very curious how they'll pivot and handle this holiday. At that point the presumably impending Switch successor release might mean a price cut to drive holiday sales, or the introduction of $30 Selects perhaps, but I expect the latter is least likely since the evergreens will presumably continue to the next system.
Anyway, all this is to say I suspect they've had a plan for this scenario for a long time and that it may mean a cross-gen game that was to be marketed for both systems will be released for Switch this year. It's really hard to suss out but I just don't think they're going to leave the back half of the year open exclusively for remakes. And I see my hopium, lol. I just really want a great DK and it's hard to picture that not being overshadowed by a new 3D Mario next year.