I think role quests present a great opportunity for new story telling for the jobs while allowing the Dev's to keep up with the ever increasing number of jobs.
What I hope they do with them in 6.0 if they intend to keep them is have the jobs come together in larger plots.
For example, something so great that black and white mages need put aside their differences and pull together to stop the threat, Red mage has to being them together, bam, caster role quest, it works with new game plus as playing it as one of the 3 would give you a different perspective.
I think something like that would be interesting, would love to see Paladin's and DRK's having to coexist.