There are so many IFs here.
IF Turkey joins the EU - which even if it happens, is a very long way off as most of the EU is against it, and many would have to get it through a referendum for it to happen (which it is unlikely to pass).
If that happens, these figures assume there wouldn't be transitional controls. We had these when Romania and Bulgaria joined, and it's hard to believe we wouldn't if any other countries joined.
So IF this happens, it's at least a decade away and more likely two decades. By which time the Turkish will very different to now - rendering any predictions about how many might come here irrelevant.