I can't help but think that the time for Arnie to do this has come and gone. It'll be interesting to see how, if at all, he gets back into shape for it. I do like the idea of an older, grizzled Conan, like we saw at the end of CTB but really, I think the time to have done this was 10 years ago or so, when Milius was shopping around his King Conan: Crown of Iron script (or whatever it was called).
Also, as Admiral Young
points out, this isn't a reboot. I'm not sure what you'd call it where they return to the original continuity (assuming that this is a sequel to CTB, albeit one which ignores The Destroyer). A revert?
The nearest similar examples I can think of are Superman Returns and Never Say Never Again. Neither is on all fours, as SR was (infamously) a 'loose sequel' to the first movie but with a different cast, while NSNA was a remake of one of Connery's earlier 007 movies.
While Conan has a certain cult following, it's not as popular as The Terminator or other signature Arnie roles and I'm not sure how big an audience there will be for this.