No, if you revert back to the current release, you can load any pre-beta save. It is just that the current release will not be able to load saves made in the beta version. I'll clarify that in the original post.
There is a possibility of loosing progress during the beta, if there are significant changes made that would make maintaining beta to beta save game compatibility unfeasible. On the other hand, if only minor tweaks are made, there could potentially not be any progress lost (don't know if or what further changes are planned before the general release).
It would probably be a good idea to create a new profile for the beta and then copy your latest save folder there, so you will not overwrite any current quicksaves or autosaves, etc.
