Bioware’s Stephen Read has tweeted that the Beta client will be usable for anyone with early access.
FAQ: if you played this weekend you do NOT need to uninstall the #SWTOR client. We are planning to patch it to Early Game Access / Live. If you played before this weekend we will recommend a reinstall just to clean up, but otherwise no.
At least gamers who are joining early don’t have to worry about installing the game again, hopefully it will be a quick and painless process.