Sorry but I pretty much guarantee it won't be Sinnoh remakes, Z, or Delta Emerald. Sinnoh = #2soon, Z = not as much cash for the same thing. Delta Emerald would be just silly right now in all honesty.
I COULD see Gen 1 remakes... but I still doubt it will be the case.
It's known for a fact it will be a PAIR of games being released for Gen 6. So it's going to be X2/Y2 // XZ/YZ // AZ, what have you. Sequels or something somehow related to the Kalo region and the Pokemon there.