Another reason sport climbing seems to be dominating right now as the primary medium for advancing climbing difficulty is that most hard sport routes - Dreamcatcher, Jumbo Love, La Rambla etc - are enhanced to some extent, usually just enough so they're feasible for whatever the current elite level of climbing difficulty is. Bouldering, on the other hand, has to wait for standards to advance to the level of difficulty the rock actually presents, because of the stigma attached to manufactured boulder problems. In this sense one could argue that the advances in standards seen in sport climbing in recent years aren't really representative of an actual advance in difficulty, compared to the way that bouldering standards have advanced. In other words, if you were to apply the same strict, no-fake-holds standard to sport climbing that you do to bouldering, sport climbing almost certainly would not be where it is today.
I think the next real advance in sport climbing will have to wait till we get people who are trained up to Sharma's hypothetical "8a problems stacked on top of one another" level, which no one, including him, is anywhere near yet. The training technique and human ability for that probably doesn't exist yet (if it ever will), and in any event the current prevalence of manufactured routes on the cutting edge of difficulty hinders, not advances, accelerated difficulty. The fact tha Sharma himself has only advanced 3 letter grades since in the dozen or so years since Necessary Evil could be taken as proof of this hypothesis.
