Sorry, I didn't see your message until just now.
The beta is here: Toad for Oracle 15.0 Beta
BTW, the numbering for it is going to change - it's 15.0 right now, but management changed their minds on the next version number. So the next time beta is updated, it will be numbered as 14.1 instead. It will be the same code, just a different number. But you'll have to deinstall 15.0 (if you installed it) and then reinstall 14.1.
And there is a list of the fixes/improvements (so far) in the beta here: Beta Released (15.0.23.720)