F-15 Service Life Question

I have read on most military websites that even though the F/A-22 Raptor will be introduced in 2005 the F-15’s could still be around until 2020-2030. The Air Force would have to upgrade the airframe, radar and engines on the current F-15’s in order for the F-15’s service life to be increased from 8000 hours to 12000 hours. To upgrade all the current F-15’s to a 1200 hour life span would cost about 3billion$. So far the Air Force has made no decision, but I’m thinking that since they will only get about 339 Raptor they will be inclined to upgrade the F-15.
What do you guys think? I personally want them to upgrade the F-15’s, or else we would only have 339 air superiority fighters. Upgrading the F-15’s would increase their capabilities as an air superiority fighter. With the 12000 hour service pack the F-15 will be around until 2025, by then the 6th generation fighters come out and we can retire them without any concerns.