I believe that whole legions of pro-life conservatives will withhold their vote if your prediction comes to pass.
I believe that hyperbole is probably total baloney. I am a pro-life social conservative Christian, who is EXTREMELY disappointed in some of Guiliani's positions, and especially some of his social behavior. Nevertheless, I am weighing his candidacy on the totality of the situation, and unless the political landscape changes drastically, we will still be somewhat divided in 2008. With control of both chambers and the WH, the GOP is going to get unfairly blamed for many of the negative things that happen in the next 4 years, and another presidential win will likely again be won only through a tough fight. Thus we may be forced to choose the nominee with the best chance of winning in the general rather than closest to my positions. Rudy easily has the most crossover appeal of any current realistic potential candidate (though certainly an unknown could emerge), enough that would likely more than cancel out the "sit at home because I prefer suicide to compromise" crowd.
Not to mention that if Bush is successful in naming 3+ strict constructionists to the USSC, including the replacement of at least 1 liberal, than abortion becomes less important as an election issue. Plus I think he can moderate his position on guns.