It would be the same as Gen 4's Transfer to Gen 5. A different Minigame, but it would still be the same process.
As for "need to remake gen x cause of system y", as I stated, transfer isn't an issue. Between Gen 4 and 5 all of Hoenn's Pokemon are available. Only ones missing from Gen 5 are Starters, Weather Trio, and the two Download only Event Legends. If they don't have Gen 4 games, they can easily buy them at Gamestop or some other small time Game store, or online. Can't rule them out cause people don't have them when the current handheld still plays those.
Only reason Gen 3 (which is both Hoenn and Kanto) need remakes are for the stories.