I would not mind seeing lunar transformation's down the road but im going to have to agree with Longknife on this one it would probably be to risky to mess with the Questline like that. Maybe a future DLC hopefully but i doubt it.
I also suspect they've run into problems implementing werebears.
Why? Well similar reasons, but also they've already made a lycanthropy perk tree attached to Dawnguard.
The problem? DLCs can't reference each other. For example Honest Hearts for New Vegas had a much-loved perk called Grunt that effected more modern firearms (no revolvers or older firearms) and made them better. Unfortunately, many guns from other DLCs that would be viewed as modern firearms weren't effected by it simply on the basis of DLCs not being able to recognize each other without potential for bugs and crashes.
Now that they've given us the lycanthropy perk tree via Dawnguard, that means that if Hearthfire or hell, even the base game offers werebears in the future, it most likely will NOT benefit from that perk tree. They have to make a seperate one for werebears, which might be odd considering the perk tree would basically be named "Lycanthropy Junior."
Or maybe we simply WON'T get werebears...