It really depends on what you mean by "futureproof", hence why I hate using it to describe technology. However, to clear things up I will use it.
If you want a system that will overclock well and allow you to add in some 4GB DDR3 RAM sticks in the future, then the i5 (and i7 s1156) are very "futureproof". Also, the performance of i5 and i7 chips is very good, certainly more than modern games can make use of - so in terms of gaming a CPU upgrade will not be needed for some time. With this kind of definition, then the i5 should be just as "futureproof" as your old s939 system.
However, there is another definition of "futureproof" which relates to the platform continuing to be supported and developed on my the manufacturer. For example, will the new 32nm 6 core Intel CPU come to current platforms? In this case, s1156 (H55/57, P55) will not be able to take these upgrades (as far as intel has revealed), but the more expensive S1366 (X58) will accept upcoming intel 32nm hex cores. On the other side of the lines, the AMD AM3 platform looks like it will be arond for some time, and accept their new Phenom II Hex cores. If you go by this definition of "futureproof", ie likelyhood of supporting future processors, then the X58 or AM3 platforms appear to be the best.