Meh, I really hope they don't. If they did it would completely change the format AGAIN, then we'd have SPs, AND Holon's running amok. So I really think they should wait for quite a while before they do that.
Nice idea, but I think the deltas are gone for good. :[ They advertised Dragon Frontiers as the last set containing delta Pokemon, but who knows what might happen in a year.
Hmm, that sounds like a cool idea, but I'm not sure if it would happen. The Holon Phantom set was cool. I'd go out and buy a bunch of packs if they did remake something like that.
WP
While I personally liked the Delta Species, I don't think they'll be returning. We already have a delta-esque concept now, that being Pokemon-SP. Also, I have a feeling they will remain exclusive to the late-EX era...