The F-15 is still in production for South Korea but I think the US has stopped procurement.
We're building F-22's now. We'll see, but that may turn out to be just as dominant as the F-15 was.
You can have three of this or that, or six of another for each of what we put in service. Go for it. I'm pretty confident we'll still have what we need to win against anyone, if it ever comes to that. Certainly for the foreseeable future.
BTW, did you see what the Israelis have done with the F-15? IMO, we should be doing this too and probably will. Check out the F-15I. Of course, the IAF are just a bunch of bozos too and don't know what they're doing. Right? I mean, they have no experience fighting Soviet equipment do they? No wonder they buy the wrong stuff!