Ironically and in theory it may well actually have some advantages for gaming as well.
Let's assume that it is a golden of golden bin optimized chip (otherwise you would not have 12 cores, ALL working, and yet it meets the TDP with all 12 cores running at full blast).
Also assume the purchaser overclocks like crazy, BUT would never de-lid, and that this 12-core has a soldered TIM (almost certain, as TDP is too big for other TIM).
If the game expects/uses 6 cores (i.e. is ready for the Hex core 2011's), only half the cores are used, but that means that you can get the full turbo boost (I guess), overclock like mad (its a very good binned part, and only half the chip is being used, so much less heat generated, and great soldered TIM, and double (approx) the heatsink area, if that helps, as 12 core is bigger than a quad 4770K).
Additionally the cache (I don't know what size it would be) will be a top end xeon (like) 12 core version, which can add e.g. 5% speed up. (I.e. it will be a giant sized cache (ready for 12 core Xeon), compared to 4770K, in theory).
The memory will also probably have more channels and allow, hopefully the fastest methods/speeds, available.
It may have some additional IPC speedups, in the same way socket 2011, gets some, over the basic architecture (advantage of being a LATE version of the architecture).
CONS: it is an older architecture, than the latest one (usually).
BIG CONS: Most gamers, are NOT going to pay around $2000 to $3500 for the cpu.
(But if they also use the computer as a workstation during their day job, it could be duel use).
Sooner or later, I would imagine games would exploit 12 or more cores, but it may not be for a very, very long time. (I.e. We are not going to see 350GHz single core cpu performance and 100x the instructions per clock, for single core/thread operations, unless there are major technological innovations, and maybe if the laws of physics would give use a break, starting with the speed of light, and the size of silicon (etc) atoms).
A more realistic proposition, would be to make the 8 core Haswell-E chip, come in a super extreme eddition, which allows ALL available cores to be enabled (unlocked) by the user.
So if you buy the 6 or 8 core, you can unlock all 15 (or however many there are on-chip), and if you are lucky get more than the 6 or 8, that it came with.
This should not directly cost Intel any money, because the cores are already there, which may or may not work, and it is the most expensive chip which Intel sell to enthusiasts.
Serious use business customers should be going for the pricey high end Xeons (there are cheap ones, I know), and NOT overclocking (or unlocking cores).
Some business might be lost, so what I describe is NOT clear cut, but should be workable.
E.g. We generally see business's buying xeons (for their higher end computers/servers), rather than buying 4670K/4770K and messing about, overclocking them.
Also very high end business's, with high end servers are multi socket cpus, so unlockable cores, on a single chip (max 1 cpu) would have less impact.
EDIT: N.B. Above is speculation, and a de-lidded 4770K, wildly overclocked (and with a big dose of LUCK on how good a 4770K you manage to get) + water-cooling (maybe), could well have better gaming performance.