a series anniversary doesn't focus on the starting show
I'm surprised Pokemon is the only one doing this. Kamen Rider and Super Sentai for instance never did this on their anniversaries.
Agreed, for example when they celebrated 10 years of the Heisei Riders they did Decade and celebrated all season leading up to Decade and they did that big movie with OOOs to celebrate Kamen Rider 40th anniversary with included all riders from the first right up to OOOs who was the then recent rider.
Sentai also did something similar with their 35th with Gokaiger.
Heck I even mention Sonic Generation celebrating 20 years of Sonic and when Doctor Who celebrated its 50th anniversary they did something completely new with the then current Doctor.
So I am sorry but Game Freak and The Pokémon Company is being a tad bit bias when it comes to gen 1 and completely missed the point of celebrating 20 years of Pokémon as a whole.
The sad part is they they will probably do the same when it comes to the series 30th anniversary and do nothing when gen 2 or that matter the other gens 20th anniversary comes up.
So what does everyone expect for tomorrow?
New Pokémon, New Alolan form, the starters evolution and a bit more about the story.
They could always include special areas to receive those Pokemon in future games and/or come up with some sort of migration/importation reasoning.
Could be a perfect reason to bring back Safari Park and have these Pokémon be in there along with future regional variants they may do.