It completely depends on each group's willingness to continue to enjoy 3.5's strengths, and deal with its drawbacks. If their tolerance for 3.5's quirks is reasonably high, they won't go anywhere. Whether you enjoy the rules or not, it can't be denied that [notranslate]Pathfinder[/notranslate] is a strongly supported product line. Based on the playtest material to date, I don't foresee 5e becoming our "go to" system of choice. It may sneak in as a "rotation" player every so often, but even that is no guarantee, considering our primary GM's game of choice is GURPS, and mine is Savage Worlds and Fantasy Craft.
For this to really happen, D&D Next has to do SOMETHING uniquely different and BETTER than the other d20 derivatives. In all honesty, this whole idea of Next being the "middle ground" for all editions is probably the best road it can take--other than saying, "This is the most polished, streamlined, non-broken version of the 3.x rules on the market backed by the full support of the industry's leading business entity."