They didn't say making a two-hander would be too much work for Frost. In fact, the new trees are supposed to support 2h Frost as well.
Enhancement is different, though, and I can see where that would be a problem. So much of the tree is centered around dual-wielding, they'd have to rebuild it almost entirely just to support a 2h spec. Shamans don't feel right with a 2h weapon, anyway, and haven't for a long time.