Is the 3600 future proof?

Is the Ryzen 3600 future-proof because the PS5 and Xbox Series X should also get an 8 core CPU that are on the level of 3700X?

Yes of course.

Total, and you can upgrade it later…

6 Cores and multi-threading will definitely be sufficient for games in the next few years. The CPU loads for games are becoming less and less important.