Or maybe, just like they said, he/she's a new character by every definition of the word "new".
It is speculated that the six new stages might also be just ports from SFxT, but the recently released announcement trailer (shown at the end of this article) doesn't show any of the new backgrounds to either prove or disprove the speculation.
Ultra SFIV can be bought either as a digital upgrade to your old SFIV (and SSFIV or SSFIV:AE) discs worth $15 or as a full game disc worth $40 that includes more than $40 worth of DLC. If pre-ordered, customers will get UDON-designed alternate costumes for the five new characters for free.
The game is due release on early 2014.