Unless they completely ditched the module concept then there will be some MT penalty even if it's less than 20%.
Unfortunately the gap in the server roadmap suggests that there may be no 4 module FX Steamroller. Also would be odd for there to be desktop Kaveris with more than 2 modules while the server APU is listed as only 2.
I did some guesstimations a little while back on what a 3 module Kaveri might look like performance wise:
http://forums.anandtech.com/showthread.php?t=2321195&highlight=
There won't be 3 module kaveri, do you people even understand. There is a gap, currently there are no 6-8-10 core high end server chips on AMD's roadmap involving servers and that does not indicate AMD's desktop roadmap.
Just because they currently only listed an quad core APU with Steamroller cores that does not indicate that there won't be Steamroller FX.
This is like the thing with broadwell, everyone expected it to arrive to desktop while it did not. This is the oposite situation.
Everyone claims it won't arrive and then it arrives.
@intel17
"Ivy Bridge-E will make short work of anything AMD could put out in the Enthusiast space."
Overclock FX 8550 to 5Ghz and its close and cheaper
Update:
Ivy Bridge-E is a 6 core, right? So it should score 11.4 to 12.0 points in cinebench 11.5 multi-thread if its clocked at the same clock speed as i7 3770k thus a Steamroller FX 8550 should beat it or be just slightly slower than Ivy Bridge-E in multi-threaded.