The sales of Wiz 8 would be a guide only - it is by no means an absolute measure. There is no rule of marketing stating that the first version of a new game series (lets face it Wiz 8 is so different in interface and playability to previous Wizardry games that it is in many ways a new game)has to be the highest seller in the series.There is no way Wiz 9 is going to happen if we the players do not show any support for it.
A pole on this forum would be just a litmus test and hopefully a teaser to Sir-tech (or others if Sir-Tech haven't got the vision or marketing grunt to pull it off)to show that there is a demand.