You "probably" won't need Vista for your work as many a college won't mass update their systems until later. Of couse, most newer system provide Vista coupons to have the OS upgarde at a later date, so you're not out of its possible use later anyways. SO, if it rated Vista compatible a show of it ability later. Pricing, should remain flat even with Vista as part of it, I don't expect any great price increase as Vista is of itself will be the selling point just to push new systems.
But, if you expect some price decrease, that will probably be on the XP side loaded OS or slightly older, slower, or entry levels systems. Already XP OS alone as full retail versions is showing pricing to lessen stock levels.