I have some speculation on new forms for old Pokemon. From the wording it seems clear that if an old Pokemon has a new form then it must be in the Alola dex (as in not restricted to only the national dex). So unless the Kalos region is also contained in these games it seems likely that in order obtain the previous forms of the Pokemon one will have to import them via Pokebank. it should be noted that when breeding two different forms together the hatched Pokemon would likely take the form of the female like is the case already with Basculin and Shellos.
I couldn't find a list anywhere, so apologies if this information is located elsewhere and I missed any Pokemon, but I watched all the English and Japanese trailers and made a list of the old Pokemon that appeared in them.
Assuming this is the case then there is another contradiction with the leaks due to the appearance of Arcanine in its usual form. This is a big assumption, but assuming Arcanine is in the Alola dex then it seems likely that they would use its Alola form in the trailers.
So I am not going to put much faith in the rest of that leak, especially fighting type Abra. Please Gamefreak don't do this! Alakazam has been one of my top 5 favorite Pokemon since RBY and I always use him whenever I have the chance and this is one change I don't want to see happen. Mega Mewtwo X was bad enough.
I couldn't find a list anywhere, so apologies if this information is located elsewhere and I missed any Pokemon, but I watched all the English and Japanese trailers and made a list of the old Pokemon that appeared in them.
It would seem likely that many of these Pokemon are native to the Alola region so there is a very high probability that they will not be getting alternative forms. I don't remember how it was in the reveal of Pokemon X/Y but I believe that all of the Pokemon used in the pre-release trailers were available to be caught in the Kalos Pokedex. Most certainly the Pokemon shown outside of battle will not be getting alternate forms so no Tauros-A.In Battle
Fearow
Pikachu
Zubat
Psyduck
Primeape
Arcanine
Machamp
Slowbro
Gengar
Kangaskhan
Electabuzz
Tauros
Eevee
Snorlax
Dragonite
Ariados
Sudowoodo
Politoed
Murkrow
Delibird
Skarmory
Masquerain
Nosepass
Flygon
Milotic
Salamence
Metagross
Garchomp
Lucario
Lillipup
Gigalith
Krookodile
Archeops
Emolga
Rufflet
Pancham / Pangoro
Sylveon
Goodra
Trevenant
Outside of Battle
Charizard
Slowpoke
Tauros
Lapras
Miltank
Sharpedo
Stoutland
Assuming this is the case then there is another contradiction with the leaks due to the appearance of Arcanine in its usual form. This is a big assumption, but assuming Arcanine is in the Alola dex then it seems likely that they would use its Alola form in the trailers.
So I am not going to put much faith in the rest of that leak, especially fighting type Abra. Please Gamefreak don't do this! Alakazam has been one of my top 5 favorite Pokemon since RBY and I always use him whenever I have the chance and this is one change I don't want to see happen. Mega Mewtwo X was bad enough.