Looking into it, there are a few possibilities. Heracross, Hitmonchan, Hitmonlee, and Hitmontop are some of the only remaining Fighting-type Pokemon who aren't in the game. It will probably be Heracross since it's just advertised as one reveal, but who knows, they might surprise us. Might not even be a Fighting-type.
Ya. considering it has a mega evolution it also means it's got more of a chance.
I'd really like to see heracross in the game, but i'd really like to see slowbro (most likely not going to happen tho) and kangaskhan in the game (both have megas and ra in their names)
just doing a quick search, these are the pokemon who have megas and ra in thair jpn name;
- slowbro
- kangaskhan
- gyarados
- aerodactyl
- heracross
- tyranitar
- swampert
- sableye
- aggron
- manectric
- latias
- latios
- groudon
so all of those have a god shot at getting in, too - but just because they have a mega doesn't mean they're gaurenteed to get in, since we have plenty of non mega pokemon.
that said, out of those, i dont think slowbro, gyarados, swampert (since they just revealed sceptile), lati@s, or groudon will be the pokemon in the game. the others have a fair shot at getting in, but i'd say tyranitar and aggron have a lesser shot since dragonite is like 10/10 perfect fighter, but was made a support pokemon - that's just my spec tho.
Now out of pokemon who don't have megas but have ra in their jpn name (not listing every pokemon, just the ones who I see getting in the game);
- kingler
- marrowak
- hitmonlee/chan/top
- granbull (probably my bias talking here)
- raikou (tho i doubt it b/cos suicune)
- flygon (could see this happening to appease to butthurt fans upset over no mega)
- luxray
- rhamprados
- honchcrow (doubtful)
- hydregion (think this might be the same case as aggron + tyranitar)
- tyrantrum
if it's not any of those i'd be pretty surprised (tho i did list the majority of fully evolved pokemon LOL) - i just didn't list legends.