Is there already a ETA for Purity//FA 6.5 / 6.6?

6.5 = last release of 6.4. Which I think wraps up in the next month or two. So 6.4.11 (guessing) would be 6.5. Once 6.5 roles out the next month would be the first 6.6 release

Yep! Cody is right. We're working on 6.6 to start rolling out in the next few months.