I think the 'average' consumer will stay away from Win7 at first, unless it comes installed on their new PC, of course.
Those of us who follow technology will be quicker to adopt (as usual) because we have installed every released/leaked build and have enjoyed using Win7 for the most part. Pricing will play a big part, due to the economy at the time of release. Sales will pick up in 2010, I'm sure.