If you are using more than one high end graphics card then the upgrade makes sense. If you are using even say, a single GTX 980 Ti ( like me ) then the gains will be small in most cases. Some games are CPU bound and they will benefit but the number of CPU bound games is smallish. Personally I need more SATA ports and would like to use my 980 Ti in a PCI-E 3.0 ( really matters very little in all honesty ) slot for maximum potential. I also want to add an M2 SSD.
If you have Ivy on a Z68 or Z77 motherboard you will find less reasons to upgrade than me. Or if you just want to move to a 'K' series, unlocked processor to overclock. Sandy Bridge users like myself who need more features and people with older systems will see the best gains. But it's your money and if computers are a hobby like with me that's often a good enough reason to upgrade!