Paying hundreds of dollars now for more for performance that you don't need now is not "future proofing". There is always a very high premium to paid to move from the middle of the performance curve to the high performance side of the curve, especially in regards to CPU.
If you convert this into a math problem, at retail prices, you are paying $550 a year for the i7 over 4 years. That amount will let you replace the i5 after 3 years and about month. NO ONE know what the future requirements will be because no one can predict the technology beyond about 12 to 18 months. Future Proofing out 3 to 4 years seems very unrealistic.
If you just want the i7 and money is no object, great, get it. If you need it get, get it. But calling it "future proofing" just seems wrong.
PS. If money IS an object and you plan on trying to keep the MBP for 4 years, it might make more sense to get the i5 and upgrade the HD AND the memory in a year or 2. I'd be willing to wager that in 2 years you can add a very fast 1TB HD and another 4 GB of memory to the i5 for the cost of the i7 today and the i5 will out perform the i7 in general.
'Future proofing' may be overstating the case. What you are buying is longevity and versatility.
With an i5 you will always be left wondering if what you are doing would be faster or better with an i7. No such worries if you buy an i7 to start with.
If all other things are equal, an i5 owner will eventually have to upgrade sooner than an i7 owner.
And IMHO if you keep your MBP for several years, sooner or later there will come a point when you want to do something and an i5 won't be *quite* up to the job but an i7 will.
And I don't believe the differences in battery life and 'heat' will be anything more than negligible, in real life.
As for 'not using' the performance bonus, you could say the same thing about people upgrading from Core 2 to i5. How many of them are *really, really* using all the performance gain? Maybe there was no point in them buying an i5?
i7 = a small price to pay to make sure your machine lasts as long as it can and can do as much as it can, processor-wise.