Not just yet for me. Not because I am playing TS4 but I am still playing TS3 and enjoying it very much. It has all the content and gameplay I currently want.
The problems will come as time goes on as TS 3 is a 32 bit legacy game which is no longer supported unless you use Origin. I do not. Therefore I do want to see TS5 but not until I am sure the company can do considerably better than it did for the launch of TS4. I have a very long list of requirements for TS5 and unless the company can show me a decent base game that is as content rich and immersive as TS3 then I will not be investing. EA needs to take a long hard look at the direction the franchise was taken with TS 4 and to do much, much better with TS5. I don't mind how long it takes because another rush job will not do this time.