Well, uh.. that didn't quite go that way for me.
The Pro 'transition' was a miserable experience that made me stop using it altogether* - it literally popped up asking me if I wanted to subscribe to Pro, and if I said 'no' (thinking I'll just continue non-Pro) the whole app quit.
* Coincidentally I tried it out again (seemed to get a 14day trial even though I'd used it before) a few days ago. There's still lots I like; the Basic tier is exactly what I needed really - last year when it suddenly held my emails hostage (slight hyperbole of course, there were still copies on the server).