I really don't think he will start unless Sanchez gets hurt.
How can he not get hurt with the current OL? The first few games have the toughest defenses, it's like last year with the Ravens opener all over again, then a few more tough defenses guaranteed to hurt Sanchez. Then Tebow will waltz in and be the hero with the easier defense and even if they continue to lose, people will have a reason to tune in, or go to a game - all the mgm't cares about.
Let's see what takes place during and after preseason game three and let's give Mark at least game one in regular season before we bash him and insert Tebow! Maybe he will start a game down the line...after our season is in the dumper, but I strongly doubt before that