There are so many issues with this question.
First off, had Pearl remained the coach, the sanctions for the program would've have been more severe. In large part, UT dodged major bullets from the NCAA because the major culprits for the violations (Kiffin, Hamilton, & Pearl) were no longer apart of the University. So that has to be factored into any question like this.
Secondly, anyone who thinks that we would've been Top 25 last year is greatly mistaken. I know we like to view Pearl as the savior, but last year's team (2011-12) just had a severe lack of talent. The perceived level of talent was so bad that the team was picked to finish second to last in the SEC by the Coaches. I know lots of fans think Pearl would've "coached em up," but it's hard to believe if Pearl, who only went 3-5 with a squad of Hopson, Tobias, Goins, B. Williams, and Tatum would've fared much better with the likes of McBee, Golden, etc. as your starters. Pearl was great, but I think Top 25 is a great stretch with last year's team (especially considering he probably would not have had Stokes--CCM recruit/commit).