These are now available to pre-order at Play.com - released 3rd April. They are a bit pricey, but have very impressive reviews and have been hard to obtain in the U.K. with many people buying them from the USA at around £190.00. Quidco available, too and the 5% discounts available to make them a little cheaper. If you love your Xbox 360 and want to spoil yourself..............Don't just vote cold because you think £130 is a lot for headphones. These are good price compared with elsewhere and I can't find a single review that thinks they aren't worth it.
From Play's website - 'The Ear Force X4 is the next-generation of Xbox 360 wireless headphones designed by the experts in gaming audio technology - Turtle Beach. The core design of the X4 is based on the popular Turtle Beach Ear Force X3 wireless Xbox 360 stereo headphones. Both the X3 and X4 use infrared wireless technology to transmit the game audio, however the X4 has many improvements, including a more powerful transmitter, headphones designed for greater comfort, and Dolby 5.1 channel Surround Sound to reproduce 3D positional sound cues that are otherwise obtainable only with surround sound speakers.
The X4 transmitter includes a digital signal processor (DSP) with an optical digital input that connects to the Xbox Dolby Digital audio output. The DSP decodes the Xbox Dolby digital stream into 5.1 channels and then uses Dolby Headphone post-processing with Head-Related Transfer Function (HRTF) technology to create realistic surround sound on the X4 Headphones. The result is an astoundingly accurate surround sound experience with the freedom to move around with wireless headphones. A unique Bass Boost sub-woofer filter network accentuates low frequencies for deep bass response from any type of input signal - music, games, movies, etc. - regardless of whether or not the source has a sub-woofer signal.'