Congrats, Shark. I really hope it does well.
That said, I guess I am going to have to play devil's advocate on a issue that I am certain may be a factor.
12 - that is twelve 20th level epic characters?!?! I really don't know if that is going to be a negative factor against it when it goes on sale.
I got players who are not comfortable playing more than one character - too much to handle in roleplaying. I've got some who can handle two characters. I think all of my players would be far too challenged to do three characters apiece, justice.
Having NPCs make up the rest of the party if people play one or two character apiece is not going to be a well received option for a (hopefully this is not a sweeping generalization) majority of DMs. I, for one, can't run more than 4 persistant NPCs in a party and run the play session for 4-6 hours at the same time without going squirrelly and ending up with a migraine.
Any suggestions for those of us who are interested in the adventure but who have players who don't want to play two or three character each and a DM who doesn't want to get committed to the psych ward after running 4-8 NPCs to fill in the party ranks for 6-8 hours per play session for X sessions.