i5 2500K + Z68 is for sure more future-proof, but I'm planning on upgrading the CPU and the board in 2 years anyway. I'm not planning on using SSD, so is there any real advantage for Z68 vs H61 for my purpose?
The P67 and Z68 chipsets are supposed to support the upcoming 22nm ivy bridge processors with only a bios/firmware update. I don't think that holds true for H61, or even H67.
My guess is that the 2500K with it's oc capability would be viable even past the best ivy bridge processors.
Everybody needs some sort of external backup. For that, usb 3.0 is very good, and is not present on H61
Don't discount the benefits of a SSD. It will make your programming experience better. In time, prices will come down a lot, and sata3 will become more important.
I am not talking about the Z68 cache capability, but using a SSD for the os and apps.