I don't see how coming out with a game two and a half years after it was announced (and presumably longer since active design first began) is "rushing it."
There is a common idea that is implied, if never outright stated, that I find odd - that Wizards of the Coast is completely unable to playtest on their own, as if they need to test everything with tens of thousands of D&D players. Don't folks realize that they've been playtesting in-house all along and that the in-house playtesting holds much more weight than your feedback and that of the other tens of thousands?
Part of the purpose of open playtesting - perhaps the biggest (but unstated) purpose - is to make fans feel like they are part of the process, that it is their (our) game. I'm not saying that they ignore external feedback, just that it is secondary to their own in-house work, and that feedback is of secondary importance to making us feel like we are part of the process.
So I imagine a timeline like so (speculations in italics):
June, 2008: 4e comes out
September, 2008: WotC: "Oops, that didn't go so well. Better start a company drive called '5E ideas'."
September, 2010: Essentials--aka Slaviscek's Last Stand--comes out
December, 2010: "OK, we better start working on 5e."
January, 2011: In-house discussions and design work begins on 5e
Summer, 2011: In-house playtesting begins
January, 2012: 5e announced
May, 2012: Public playtesting begins
Summer, 2013: 5e rules 98% finalized
September, 2013: Last playtest packet
Fall, 2013: 5e rules 100% finalized
December, 2013: Publication time announced as summer, final touches on books - formatting, art, etc
January, 2014: Books sent to printer
Summer, 2014: 5e books for sale
Fall, 2014: "Uh-oh, we didn't please all possible fans in every possible way. Better start a company drive called '6E ideas'."