You shouldn't fear anything. SH3 is special considering the way its matured. GWX is soon to receive a small bug fix and there is a main content patch due for release sometime in the future. The future looks bright for SH3 really. So much progress has been made in crafting a brilliant realistic and authentic Atlantic experience. Hell over in the SH4 forum the aren't even sure whether the game is worth buying yet! To me it seems as if there are many more problems with SH4 at release than there were with SH3.
So we needn't worry. Sure there will be some bleed off but it will be well over a year before we see SH4 getting any kind of modding that could rival SH3.
Besides if you read in one thread I explain exactly why I love the Atlantic more than the sunny Pacific.
Keep up the good work wolves. We ain't dead yet.