I'll collapse from shock if Flake doesn't win by at least 5 points, and more likely 10, "sign of trouble" and a Democratic wave notwithstanding. Jon Kyl won by 10 points in 2006 against a well-funded opponent.
I agree the last 5-8 points will be hard for Carmona to get but I would consider:
* It's an open seat vs an incumbent running for reelection
* Six years of demographic shifts in a state heading towards minority-majority status
* Republicans are likely to do worse with Hispanics (SB1070, Romney, etc)
* Midterm (2006) vs presidential election year (2012) turnout differences
* It's more likely for Carmona to outperform Obama than the reverse and Arizona could trend D compared to 2008