^^ MY guess is that TG4 will be some time. And so far, upgrades have cost significantly less than other softwares.
Ill bet you that you can buy TG3 now, and use it happily for a good long while before TG4. TG3 just came out, and this thread is mostly just to provoke Matt and Oshyan to tell us some of their secrets. So I would not worry!
Sorry if this thread has made you a little nervous about buying. If I was buying new now, I would not wait for TG4. Unless Matt Or oshyan say so.