What has done in the GOP this cycle is (A) the absence of A-list candidates in the primary process, and (B) the lack of credibility their standard bearer. Mitt Romney will be the very last GOP candidate for the GOP that will not be a true "movement conservative".
The GOP is down in the polls due solely to the personal shortcomings of Mitt Romney. Romney's unpopularity has little to do with his positions on issues; it has much to do with the perception that he is man with no core principles who made a Faustian bargain with conservatives that has not worked out well for movement conservatives.
If Romney loses, the conservative base will take steps to ensure that a movement conservative who is ready for prime time will be the candidate in 2016. This probably rules out Jeb Bush, and it will probably rule out Paul Ryan, who has lost standing during this campaign. I believe that by the end of 2013, movement conservatives will be coalescing around a particular movement conservative candidate to make sure that there are no more McCains and no more Romneys.
If by "movement conservative" you mean tea-party, this is huge risk for Republicans in 2016. It's going to matter how Obama is perceived that year. If his second term is a success, I very doubt the tea-party would be strong enough force to put forth a candidate to win then. However, if his second term is a failure, GOP could win, but it's going to be a tight rope to walk in the electoral college. Could states like PA, MI, or MN be realistic opportunities for pickups?
The question for the GOP will ultimately be, how do we expand the map, and from that a strong winning coalition in Suburbia? Call it the Suburban Strategy.
We have only seen 2010 as evidence so far for success of the tea party movement and only that in selective states.
That said, if the GOP nominates a Rick Perry type, they might as well wait til 2020. If it's a Huntsman type, that would be the best thing for them.