My only complaint with the 85L is that the lens extends to focus...
Functionally it's not a problem, I just have an OCD habit of wanting all the lenses set to their smallest profile when they go back into my bag (un-zoomed, etc), and if you don't focus the 85 to infinity before removing it, you can't get it back in by turning the focusing ring.
The AF for me (on the 5d3) is a non issue... It's "slow" because the gearing has to be precise for the 1.2 aperture, but with the badass AF system on the 5d3, it's really splitting hairs calling it "slow". Granted... when on a weaker AF system, if the 85 would start searching back and forth, it was frustrating...but so far (3 weeks of 5d3 ownership) I've been nothing but pleased with the 85L
I don't think an update is necessary...Maybe IS, but that would just make that lens unwieldy and not to mention even MORE expensive.
If anything I'd make it IF... but that's not enough to warrant an upgrade