Man, if Slash really is recording for the next Guns record and finishes before the next leg starts, all that may be left is mixing and mastering. Hypothetically, that could mean we could see an album by the fall, or certainly by early next year depending on what Duff and co. need to record.
By 'and co' I assume you're including Axl?
I admire your optimism, but do you REALLY think they are at the mixing and mastering stage of a new album?!
I was speaking hypothetically. As in, if hypothetically, all Slash is going to do for the next album is record guitar parts for pre-existing tracks, then yeah all that would be left is mixing and mastering. We all know up until the reunion was finalized, Axl had another album more or less ready to go that for whatever reason he didn't put out. As recently as 2014 he was still very interested in putting it out. If, like it or not, Slash is doing something similar (hopefully more extensive) than what Bumblefoot did for Chinese Democracy in 06/07, it wouldn't take very long to finalize things following said studio sessions. Same for Duff.
And as far as Axl goes, if the idea is to release the second half of Chinese (whatever it ends up being called) with additions from Slash and Duff, I don't see Axl doing much, if any, additional vocal recording for the album. I imagine what he's already recorded is going to stay firmly in place.