If you're happy with that focal length range on a crop body, then the 24-105 is the best choice. If you could make do with a shorter focal length and slower f-number, the 15-85 would be a great option -- I would guess that it has noticeably higher contrast and resolution than the 24-105 (which is already very sharp).

It's possible that a new 24-105 could come out any day now, or it might be another 5 years. Nobody knows so I just don't worry about it. One safe bet, though, is that it will cost a whole lot more, as you suspect.