Well, at least we have some real information now. I think the struggles we're seeing here is what has been going on for quite some time.
If I am reading his comments correctly, the refactor itself has been "done" for five weeks. That would mean all of this time has been a test->fix->test cycle. If they have documented 40-50 new bugs in internal testing, it is bound to be 100s when it reaches us. I don't know how you could realize 2 months into EA that a refactor of this scale is required.
One impression that I have gotten over the months of following things is that it appears that at least some of the developers are not doing a great job of testing their code before it reaches QA. This is just a hunch but I do wonder what their processes are in terms of Unit Testing and even Ad Hoc testing.
Anyway, if Mexxico says "at least" a week, we're probably looking at 2-3. Their burn rate against "40-50" bugs is roughly 8-10 per week and there are sure to be more detected over the next week. My guess is around July 31.