"Future-proof" gets thrown around way too much.
In short, NOTHING is future proof, as there will always be new technology break-throughs in terms of hardware capabilities.
The sort of "future-proof" that most people mean generally tends to be a complete system that will still be classed as "high-end" for more than a year, so at the current time you're looking at the newer i7 chips and hexacore AM3 chips.
As Cycrow says, just because something is old certainly does not mean it isn't capable - I'm still running an old Athlon II dual core and it does everything I need it to, and that's on the "dead" AM2 chip.
Easiest way to think about it is that future-proof will mean one of two things; either it is top-end hardware at the current moment in time and will still be regarded as 'high-end' for at least a year, OR it could mean it has upgrade paths available to it - in which case the i7 x58 chipset is nearing on EOL (end-of-life) yet the AM3 chip will still be used for at least another year with brand new chips being manufactured for it, whereas the Intel counterpart will likely be on a brand new chipset.
/thread? Haven't typed so much in aaaaages