Will there be any possible buyback/fix compensation for the Q5/Q7 TDIs?

As of now, most likely a fix.

How will that affect mpg/performance/duaribility.

What's the chance for compensation?

The 3.0 TDIs should be fixable. Doubtful there will need to be a buyback.

If the fix is determined by EPA/CARB to affect power/torque, mpg, drivibility and durability, will VW/Audi pay restitution to the owners?

From what I have heard by the Porsche and Audi dealer, the 3.0's are fixable. However lost value must be considered to avoid a swath of lawsuits, so I think it's safe to say there will be compensation.

I have a 2014 A6 TDI that I love. How can I find out its value in August of 2015?