I'm not sure how long you would have to wait to see deep price cuts from Intel on the Q9550 (I'm considering one myself), but you may see a number of good deals popping up in the next month or so (think Black Friday) with Christmas approaching.
While the Core i7 920 should be released in a similar price range as the Q9550, I don't think that it will be a direct competitor to the Q9550 for some time due to the combination of relatively high DDR3 and X50 MB prices (at least for the few X58 boards that have been announced). If DDR3 prices begin to fall at an accelerated rate and someone comes out with an X58 MB in the $200 price range, this could change of course.