Thing we must all remember is that Jo is a programmer, not a director or studio manager, he's filling us in best he can. Ultimately the decision for releases is down to Matt, and nikita, what Jo's post says is that there are many VERY fundamental things that have been done to the code behind TG2. Things like multithreading have a gargantuan knock on effect with other areas of the program. I don't personally know how TG2 has been built but if it is object oriented (as I would expect these days) then every class, struct, function and variable needs to be handle effectively to be used by two cores. That's a massive thing to do and the slightest miscalculation can make one, very very well hidden, variable go wrong, the programmers then need to find that variable and fix it. This is a huge job for 3 people, as calico said, to do.
