The M2Go cannot be upgraded past version 4.2.1057. However, you can use it in USB mode with a PC running a version higher than that (4.4 and up). If you have 4.2.1057 installed, just leave it, it will run 1057 as a standalone controller still and then if you need the higher version, use the USB mode.
If I recall when they released the NXP/K you had to be running a certain version. So I doubt they would work on 4.2, which is really old. While I understand some people wanting to utilize other hardware, I would strongly suggest investing in the NXP/K and upgrading to 4.8.1244. There are so many bug fixes and improvements along with a few new features. Not to mention the Beta 4.9 RC with a major improvement in DyLOS and beat detection going through last rounds of testing before being released.
That said, you should evaluate your setup before upgrading. Make sure your fixtures are in the new library (4.6 improvements) and that your PC still meets the minimum requirements. Also if you are using any 3rd party integrations, what may be needed.