You raise a good point. No one can predict the future and there's always the possibility that manned missions may be necessary to secure our military hardware in Europe.
I do think it will be at least 10 years before China can do anything realistically threatening in space, unless you're talking about "killer satellites" which don't have anything to do with manned missions and can best be defended against with technology, not people.
In the meantime, we can keep our edge with fewer flights and fewer people on each flight while going full speed ahead with putting the most sophisticated technology in orbit that we can develop (which I'm sure we are doing).
On a return trip to Vietnam in 2000 with my daughter, we were sitting on China Beach where more stars than I'd seen in years were visible as it was so dark.
We watched what we were sure was a satellite pass overhead from south to north, so in polar orbit, an hence likely military. Given just the numbers, I said, the chances are better than even that it was one of ours.
Everything Good....