I picture things a bit different than you.
Iowa Newt and Cain statistically tied. Perry a distant third, followed Paul. Bachman might even beat Romney.
N.H. - Romney wins minimally.
S.C. - Cain, Newt, Romney, Perry.
FL. - This is hardest to predict right now, but will also be the one that starts driving candidates out. My gut feeling is that Cain has an advantage over Gingrich here, but that might be wishful thinking on my part. This could be the spot Romney bails out again.
As far as when candidates start bailing out..that's harder to tell..because all the debates enable the 2nd tier to hang around for a few more weeks each time, without needing much $$$.
S Carolina has picked the eventual winner since 1980. Eventually, they'll mess up, and get it wrong..but I have no doubt they'll get the top two, right..though not necessarily in the correct order.
S Carolina IS important..first primary in the south, and with an electorate that really reflectes the GOP base..and one more thing..both Haley and DeMin have pledged to stay neutral in the race until after the vote, ( or possible just before) and they will have an impact..especially if they agree on a candidate..
OTOH, there's still a chance that we come to Tampa without a candidate..an open convention...