Well you still have quite a handful of quests to finish, so if you found the 4.0 DRG more interesting than the NIN, go for it. You can always go back to your NIN and lvl him up or switch over to SAM. Take your time, enjoy the game and play whichever job you find most intriguing. It's always handy if you have more than one job on 60 (with SB 70) to switch if you get bored. You could also decide to step back from the game till SB comes out if you think lvl up DRG and/or NIN isn't worth the time/effort since you'll probably change to SAM.

When I started with FF14 I stayed with my DRG till HW, then around lv 55 picked up the Arcanist from scratch and played till lv ~58 as SCH/SMN when I again switched and went back to DRG, simply because I was bored after a while. Don't know if this helped, my advice is have fun and don't think about it too much.