As I said elsewhere, color me disinterested if it's simply the same class powers except with keywords. I think you can do that easily enough now with magical items or careful power choice for magic classes. I'd love to see a mechanic unique to elemental classes similar to power points for psionics - something truly unique and changes how the class is played.
I've always thought elemental classes that were forced to manage elements-as-a-resource would be pretty awesome. Utilize the fire you find/create as the source of your power, but the more you rely on it the more counters (water/cold) can hinder your options... I don't know exactly how it might work, but in any event in things like Avatar (The Last Air Bender) availability and amount of elements proved useful in combat.
Sort of like taking terrain powers to the next level, opens up some DM options and some more complex play w/o requiring epic levels to do so. Of course, I think how I'd envision it would be an entirely standalone game... but I do have faith that there are smart enough folks at WotC that could do some truly cool things within their system and make it different and better than just the same powers with new keywords. Will the right people be involved and unhindered? That remains to be seen.