Trying to future proof over this kind of time frame is impossible. A Core 2 Extreme ($1000+ processor from 2008) gets slaughtered by the $250 mid-range i5-2500k from 2011. So in three years, cutting edge processors will be outclassed by mid-range hardware. http://www.anandtech.com/bench/Product/48?vs=288
This is the most extreme example, a 3770k (which is on the line between mid and high end in the whole scheme of things) wont last near as long.
Buy a processor that will give you the performance you need now, not the performance you hope it will give in X many years. It will work out cheaper (and likely more end up a more powerful rig) to upgrade the processor when you need to.
for the present i7 3770K is worth, according to intel i7 3770K can survive for at least 5 years and it has not been proven due out this year 2012 , also it all depends on usage, which I know is very strong is P4 and core 2 duo, I still have and use in the office, and it all depends nevertheless on a good PSU
Trying to future proof over this kind of time frame is impossible. A Core 2 Extreme ($1000+ processor from 2008) gets slaughtered by the $250 mid-range i5-2500k from 2011.
I wouldn't call a 20-30% difference between Extreme and i5 "slaughter". It is solidly in "not worth bothering about" territory in my book since it is not going to make or break any game or applications for most people.
Most modern games still work perfectly fine on i3 or even 5-6 years old Core2Duo as long as you aren't obsessed about hitting 60fps and beyond.
Depends on what your needs are as well as expectations.
My primary PC was built around the Q9450 back in 2008 and I don't plan on upgrading until either Haswell (2013) or Broadwell (2014). The Q9450 has so far given me satisfactory performance for my current needs.