Due to all the changes that 3.0.0 adds, mainly around the new level stuff but some balancing things as well, the update is going to force a new save for everyone. Your old save file is still there, if there is a great enough need for it, I can upload the old 2.1.0 version so you can still play on your old save. However, I very much encourage just starting fresh on 3.0.0 and enjoying all the new features.
Boink has entered release candidate (RC) #7 and will most likely see an RC #8. But we are hopeful for a weekend launch :)
-TheKingOfLettuce