The Athlon X4 880K Specs appeared in a compatibility listing from motherboard manufacturer Biostar.
The chip, which hasn't been formally announced yet, will run at 4 GHz and will follow-up the 870K which is yet to be released.
There is no word on how much it will all cost yet, but the 860K has been seen for EUR 70, which should give you some idea.
According to the BioStar listing this is the chip's spec:
|A10-7890K, apu||Kaveri||2 / 4||4,1 / ?GHz||4MB||95W|
|Athlon X4 880K, cpu||Kaveri||2 / 4||4,0 / ?GHz||4MB||95W|
|A10-7870K, apu||Kaveri||2 / 4||3,9 / 4,1GHz||4MB||95W|
|Athlon X4 870K, cpu||Kaveri||2 / 4||3,9 / ?GHz||4MB||95W|
|A8-7690K, apu||Kaveri||2 / 4||3,7 / ?GHz||4MB||95W|
|Athlon X4 860K, cpu||Kaveri||2 / 4||3,7 / 4,0GHz||4MB||95W|
|A8-7670K, cpu||Kaveri||2 / 4||3,6 / 3,9GHz||4MB||95W|