If i was to buy an iMac then it would be i7. Better for today, better for tomorrow and better resale value in the future.
I understand those who say they want i7 for more power, etc. But for future proofing? Really? You think that in 2 years the i7 will perform better then the i5? I remember when I bought the 2,24ghz pentium 4 instead of the 2,36ghz that was 500$ more for 30% more power... 2 years later, they both sucked exactly the same.
Future proof in computer processor is irrelevant.
Buy for now, not for later. Need the i7 now? Buy it. Don't buy it for the wrong reasons.
just my 2 cents