Although today the F-16 serves extremely reliably in many Air-Forces around the globe, the introduction of the Boeing/Lockheed JSF's (Joint Strike Fighters), will do what the introduction of the F-22 did to the market and use of the F-15 Strike Eagle. I.e the gradual phasing out by the U.S.A.F and consequently, the rest of the world. The JSF may also eliminate the need for the F/A-18. This is apart from the intro. of the E and F models jiust introduced into the U.S Navy as a fighter/Tanker.
However, this generallization and Standdardization of the U.S.A.F's capabilities I believe is slowly destroying the edge the U.S had in its military against other worlds powers. This ability gave them the edge to do anything, anywhere, anytime with their high diversity of fighter and bomber roles.
I believe that this standardization will bring the gradual downfall of the U.S Military and the rise of the Chinese, Japanese, Middle Eastern and Russian world powers with thier unmanned fighter projects coming well into the foreground.
So, to summarise, I forsee that the gallant service of the F-16 over the last 15 years or so, will come to an end in the next 5-10 years. However, it may continue service in foreign Air-Forces for the next 10-15 years. But again, we must let go because all good things must come to an end.
The New General Dynamics X-35B STOVL JSF In Action