Don't count on it, Ford is ALWAYS late with new models.
The 1999 Mustang finally made it into production in Dec 1999, 4 months late.
The 2005 Mustang was over a year late from it's adjusted schedule. It was supposed to be out in 2004 for the 40th anniversary after it had already slipped a year from it's 2003 MY target, so it was really > 2 years late.
The only leaked info. that we've seen has been for the California Special. And the CS looks to be only decals and fiberglass. So other than the CS & GT-500 we know that nothing else is in store for the 2007 Model Year.
If anything is coming for 2008, the design has to be locked in within the next few months (if not already). We've seen no test mules of anything. Remember we were seeing GT-500 mules over a year ago. So this places doubt as to if anything else significant is coming before the 09 update.
The only thing that gives me hope is that over on TMS someone who works in the parts department of a Ford dealer found reference in the parts books to an updated 4.6L, 4V engine (Mach 1 motor) for the 2008 MY. So there is a chance that we will see a SE with the 4V motor for 08. It would make sense that Ford would do that, create a model to prop up 2008 Mustang sales while excitement builds for the face lifted 09 Stang. It's the exact same strategy Ford had with the 03-04 Mach 1, an SE to prop up SN-95 sales because everyone knew S-197 was coming.