According to the info I looked at, the X99 won't be compatible with Haswell-E, it will also be socket 2011, but with a different structure, so it won't be backward compatible.
Well, if they don't release an X89, the socket 2011 seems like the biggest joke on Intel's part, now they're releasing CPUs that won't be fully utilized if they don't also release motherboards and a new chipset.
I think it's a mess on Intel's part, it's very bad that there isn't serious competition because they're doing whatever they want.
This move by Intel suggests that they will soon release Haswell-E and will leave the X79 behind
right now I see a 4670k as a better option, 4770K with z87 is the most advanced from Intel.
Regards