Well. The answer is pretty simple; It is a tank.
A tank is a symbol of power and strength. You need heavy equipment to stop him. With his canon and machineguns he can still kill people.
A tank is always attractive e.g. for warlords or in regions without military strength.
On the other side nations like North Korea will use the T-34 as trainings unit (i think they will use them for training). The T-34 is simple and solid enough to train soldiers in simple tank stuff like driving a tank or get a feeling for the weapon system tank.
An the last aspect is the prize. It is still possible to get spare parts for the T-34. A fully operational T-34 without guns coast ~30.000€ at the reenactment market. So it is pretty cheap.
All in all his time is over but there is still a small gap for an old tank to serve in. A lot of nations will try to replace this old stuff with modern weapons but thats difficult. I think we will see a lot of ww2 stuff in service in the next years (look at Syria; They are using german howitzers and StG 44 from the former Yugoslavian army).