The only parts I'm surprised about are:
*The sheer amount of new content. I was expecting just a few sub-legendaries and a sub-region, but we are getting tons of stuff.
*The fact that this is going till Autumn and Move Tutors will be here. That makes me wonder a bit, since that even though we know VGC 2021 will focus Nat Dex and VGC 2022 will focus on Mascot Legends like always, the fact that we will be stuck with a single moveset change for rest of the generation is untenable.
*The fact that instead of two packs, it is one pass with two parts. That's a bit interesting, though apparently that is what they did with BotW so I should be the one who needs to correct himself.
*A Grass Mascot Legendary. What took them so long?
Everything else including the Pokémon being able to transfer regularly without paying the DLC are what I suspected will happen.
So:
*The big question is what changes will occur for older Pokémon regarding BST, Moves, Abilities, and Egg Groups. Base SwoSh was extremely anemic when it came to buffing old Pokémon, so the question is whether will this pass do the same. Stuff like Gigantamax forms and Galarian Forms only really matter in VGCs, not 6 vs. 6.
*What will be the June reveal then? We should assume the next two datamined Mythicals' in-game code will be available alongside the DLC pack, but only one should be released in 2020. What will happen to 2021 one?
*Since not all Pokémon are going to be catchable here (even though they should be transferred over if they are clever), there should be another Pass in early 2021, but considering the nature of current missing Pokémon (mostly Sinnoh Regional Dex members besides Legendaries) that would conflict with GF's traditional release schedule as well as current annual releases.
The only way out of this I can see is another Crystal situation, where DPPt remakes will be in December 2020-March 2021 range (depending on when Crown Tundra releases in Autumn) with the remakes being Switch Pro exclusive. That sounds like a nightmarish situation, but the presence of Megas in MD like in Pokkén strongly suggests that will be the case.