Apparently this guy has his info twisted.
*Asajj Ventress is a she
*Asajj Ventress and Durge already appeared in Empire
*Asajj Ventress is known to carry 2 lightsabers
*Durge is a Bounty Hunter, no Jedi/Sith affiliation
*Boba Fett/Daniel Logan has been cast since April
Sounds like this guy is way off, and is passing off his speculation as rumors.
Durge is almost totally ruled out of being the new E.U. character, by his description alone.
Komari Vosa, another 2 lightsaber weilding Sithtress is ruled out, because she died before Episode 2 apparently, thanks to Jango.
I wouldn't take any of what this guy is guessing on as truth, fact, or anything other than speculation like I said.