At the point, the mystery should be pretty clear. Then again, I figured it out after issue 2. http://www.comicscontinuum.com/stories/0601/25/xmendeadly4.htm But who knows, there are people that still believe the villain is Changeling or Thunderbird. Hell, some people at Newsarama thought Darwin (as pictured) was Changeling/Morph.
since i have no place to get comics here...can you gimme spoilers for had happen so far....and who are those 4 people???
The basic assumption is that before Xavier gathered the second team of X-Men to rescue the originals from Krakoa, he gathered another to attempt the rescue. This team, however, failed and were killed. The villain of Deadly Genesis is the sole survivor of that team, who seems to have inherited the powers of the other members. He may or may not also be the third Summers brother.
Unfortunately, due to other spoilers in certain magazines, the "third summers" stuff is pretty much a given at this point. Yeah, kinda hokey, but somewhat enjoyable read so far.