Well, half of the advice we could give you now would change with 1.20, yes. However, some things will also stay the same, so I'll try to separate them accordingly.

Things I expect to stay the same:
  • Leveling Conjurer will give you Cure. Great for surviving, even on end game content.
  • Leveling Marauder in addition to Gladiator will give you more enmity abilities to choose from.
  • Leveling Pugilist will give you a TP-based cure (Second Wind). Again, great for survival.

Things I expect to change:
  • Pugilist will also give you Accomplice, which is the best enmity generator during long fights.
  • Thaumaturge will give you Sacrifice, which is the only current heal over time effect we have.

If you were going to be tanking much before the patch, I'd say definitely level PGL to 30 for Accomplice and MRD to 20 minimum for Intimidation (+enmity trait). However, Accomplice is going away with the patch, and we don't have a lot of information on what's going to happen to traits. Anyway, you can't really go wrong with leveling Conjurer and Marauder a bit.