For those saying that the industry has to learn to develop aircraft in less than 20-25 years: What we have to do is forget how to take 20-25 years, which is strictly a post-1980 phenomenon.
The F-4, F-15 and F-16 went through life-cycles that looked like this: 2-3 years from contract to first flight; another 3 years or so to IOC; major upgrades 5-6 years after IOC. The F-4 was produced for about 20 years after first flight and is still in service. The F-16 and F-15 have not been replaced, although they would probabably have been superseded in production a long time ago had not the main source of funds been pre-empted by F-22 (20 years from prototype contract to IOC) and F-35 (probably 23-24 years).
One trouble with taking more than 7 years or so from serious money to IOC is that electronics change vastly over that time. (The first BlackBerry smartphone was released in 2003.) Another is that it is impossible to maintain design expertise or an industrial base.