Just in case people have missed this there is a survey for the new BTTF game on the Telltale games blog. 
http://www.telltalegames.com/community/blogs/id-643  
It's got some super interesting questions about the type of game it could be and what it will include.   

For example it includes. 

…November 5th, 2010. Working together, Teen Marty, Doc, and Present Day Marty finally corner the man who made off with Doc’s Time Train. While they argue about what to do with the well-intentioned time-hopper, a scary black vehicle appears out of nowhere. A familiar bulky presence steps out and confronts them. ‘Detective Tannen, Temporal Preservation Squadron.’ I’m afraid you’re all under arrest’… 
 
Now doesn't that sound interesting ;-)    

The only advice I'd like to give them is, "You remember Atari's Ghostbusters game? Don't do that". 

Back To The Future is the greatest movie of all time. I would tell you all why but it would take much too long. 
 
I would pay copious amounts of cash for a BttF game by Telltale.