Current version 2 has prices set at:
Buy US$299
Upgrade from US$99.
If that is any indication, you can expect the upgrade price to be ~1/3 retail. And of course, only Adobe can say if v3 will sell for the same price as V2.
Usually when Mfgs announce an imminent release of a new version, they will offer a free upgrade to the new version for purchasers of the old version after a certain date. To my knowledge, Adobe has not extended such an offer.
There are much different pricing structures than full retail. An Academic license is about the best way to go if you can qualify.
V3 beta is valid only until April. There is also no assurance that this will be the only beta or that April will be the release date for the final version.