Honestly, I wonder, both ways. The thing is, it's perfectly possible to import Gen IIIs all the way up to Gen V, and a ton of Gen III 'Mons have been proliferated to later generations natively. On the one hand, I'd love to hear a full-symphonic-3DS version of
this song, which is the Objectively Best Route Song in the franchise, but on the other hand, Gen III actually represented the nadir of sales for the franchise. I actually think they may just want to leave it behind and not contribute to making new players feel overwhelmed.
(Like that one guy in the main forum - poor dude just wants a Pikachu for his daughter and we're overwhelming him with choice, myself included.
)
TLDR, I wouldn't be surprised either way. A remake is an "obvious" route, but I can also see why they wouldn't want to be "obvious" this time around.