To be(ta) or not to be(ta)...

My project has a July 1 deadline (soft). Do I begin dev on Beta 2.0 RC3 and hope for a stable production version, or use the current version and eat the upgrade hassle when 2.0 is released?

That means only or still 3 monthes left. You may start now with Beta 2.0 RC3. And just pray the stable version will be really stable.