Are there going to be more Megas in later updates?

I feel like there are more Pokémon that need a Mega Evolution. Mega Rapidash comes to mind. A Pegasus design with the Aerilate Ability would be great for Rapidash, which isn’t very powerful on its own. True, giving it a Flying typing would give it an even bigger weakness to Rock type moves, but if done right it could still be a powerful Mega.

Also Dragonite and Goodra are the only Pseudo-Legendaries without a Mega and none of the Sinnoh, Unova or Kalos Starters have a Mega either (even though Ash Greninja is just a Mega-Evolution without a Mega-Stone), whereas all of the Kanto, Johto and Hoenn ones do.

No, future updates will only have bug fixes and maybe sprite updates.

Darn. What about the Battle Frontier?

No content updates. Things like the possible challenge championship rewards may be fixed though.