So wait, let me get this straight. We have the main gimmick, that turns a Pokemon into a crystal form temporarily. We have standard regional forms like Tauros and regional evolutions like Dunsparce, but we also have "rfakes" where it looks like an old Pokemon, but has a separate dex number and name (Amoongus and Jigglypuff). And then there's Ancient Forms as well? I don't remember seeing those leaked.
I imagine it's not a coincidence that the number of new Pokemon dropped by a lot once we moved to 3D too
Actually from what’s being said by the leaks Dunsparce is getting a new cross-gen evolution and not a regional evolution.
The difference between Cross-Gen evolution and Regional evolution has is this:
Regional Evolution: a new evolution that evolves from and is exclusive to a regional form(examples: Obstagoon, Sirfetch’d, Overqwil, Sneasler).
Cross-Gen Evolution: a new evolution for a existing Pokémon( examples: Kleavor, Wyrdeer, Ursaluna, Sylveon, Scizor, Gliscor).
Also new prevolutions tend to fall into the category of Cross-Gen Evolutions.
In regards to Regional Fakes from what is being described is that their completely new Pokémon that just happened to resemble some existing mons.
So basically the Regional Fake that looks like a Amoongus is not a new form of Amoongus but rather a new Pokémon that just happens to resemble Amoongus do to convergent evolution.
I’d imagine that since this seems to be the case that means that Regional Fakes could potentially have new evolutions and prevolutions that don’t resemble their counterparts at all.
Now I don’t know if the ancient/future forms are the same thing or a part of the Regional Fakes or if it’s a completely separate thing.