Imagine a Super Smash Bros. Melee HD with online. Imagine.
I'm not ruling this out, but I'd expect SSB4 to come out first.
Especially if SSB4 is criticized for being too casual, I might expect Sakurai to feel guilty and throw us a bone. He's already acknowledged and apologized about Brawl.
Really, this is the HD port. With a solid online system, this game could go on for a very, very long time.