Probably sometime after it is on the test branch and everyone is talking about all the changes and spoiling everything.

It should be obvious at that point.

Edit add- If you want to guess.... then I would assume 3 months on the test branch.

Now three months while they are working in full swing. They take a month off for summer as is standard work practice where they are. And then a few weeks to get back in the swing of things.... so...

I doubt they will test anything before summer break. My total guesstimate would be about a month after the summer break they put it on the test branch? If it is ready by then? Then actually be ready 3 months after that.