So long as Square set some ground rules on skill trees (like never having us choose between damage and utility, damage will always win), there's potential for skill trees to allow us to choose between the different gameplay styles we liked in the past, as well as offering us new ones in the future without having to gut our current playstyles in the process. It could let us choose between DoT Scholar or Broil Scholar, Elemental Mage or Glare Mage, Nocturnal Astro or Diurnal Astro, etc.

It'll never happen, but one can dream, and I think Grim's right in that adding 10 more levels and continuously tacking on abilities is reaching its breaking point. People who enjoy current DRG are likely to get something very different next expansion because there's not much more they can do to that kit. Even PLD when this expansion launched only got upgrades to already existing abilities and had to consolidate Confiteor into a 4 button combo simply from lack of hotbar space, all it ended up doing was replacing a 1-2-3 in the rotation because there really wasn't much you could do to improve that kit without having to remove other actions. And all I expect for healers is yet another oGCD with a 2-3 minute cooldown and Glare IV.

I would agree though that the different jobs should be the different "skill trees", since it allows Square more design space in how they can vary up the jobs and playstyle without having to work within a shared base kit. As much as I can dream of skill trees for jobs, it'd lead to another SCH/SMN situation that made it annoying to balance, only now on EVERY job.