In the 3D era? That's WAY too much work, even for GameFreak.
Why? I mean, they managed to make six hundred and seventeen move animations for XY. They clearly showed that they have the capability to create move animations in 3D, otherwise there wouldn't have been any in XY either. It's not that much work, as evident by the fact that there are half a dozen hundred moves in the games already, and then some. If they remade as many as 40 moves, that would still be less than 1/15th of the animation work for moves in XY.
And the differences between the move Groudon is using and Earthquake are way too extreme anyways. Earthquake has always looked similar to that and I wouldn't believe it if they changed it.
I'm pretty sure that Kyogre and Groudon are receiving signature moves, finally.
Sorry to disappoint you here, but
no new moves are ever introduced in the middle of a generation. It's been a rule since RBY, and I really doubt they'll break it now. The reason? Those moves wouldn't be compatible with XY in battles. The games can handle tweaking of existing Pokémon, moves or even abilities between games. That has been done since FRLG, when Deoxys had different stats depending on the game it was used in. One generation later, Hypnosis had different accuracy when used in battle between a D/P cartridge and a Platinum/HGSS cartridge, than it had in a battle between two D/P cartridges. The games are made so that data can be tweaked, but it won't have any idea what to do with entirely new data, such as new moves, Abilities or Pokémon species.
"But... but... Internet era! Patch!"
Nope. If they had planned to do that, they wouldn't have included the dozen-odd "hidden moves" in XY. Thousand Arrows, Thousand Waves, Light of Ruin... all of those were added to XY, so they could be used by event exclusive Pokémon without the game breaking. Had GameFreak planned on making new moves for ORAS, they would have been hidden on the XY cartridges already. If they had decided to rely on patches, there wouldn't have been any hidden moves on the cartridges at all. They too would have been introduced by patch, instead of being put on the cartridges upon release.
In short, my money is on new animations for existing moves. The move Groudon is using could be Earth Power, Eruption or even Stone Edge. Kyogre's move could be any Ice move for all I know (well, maybe not Ice Punch).