Well from the microsoft website it says this:
The Beta will stop working on August 1, 2009
. To continue using your PC, please be prepared to reinstall a prior version of Windows or a subsequent release of Windows 7
before the expiration date. You won't
be able to upgrade from the Beta to the final retail version of Windows 7.
I'm guessing by this that it means that any version of windows 7 succeeding the beta, i.e. the evaluation copies, will continue to work. i activated my original key that i obtainted from using the beta when i upgraded to 7057 because it asked for it agian but maybe it will run out in August?