Most likely SFxT is out at 2012, and a year after TxSF...so theres plenty of time imo.

The Art of Blending Tekken With Street Fighter

On that note, at the very bottom mentioning Darkstalkers, Ono wants signatures for a new Darkstalkers game at his Twitter (he also checks Shoryuken.com for signatures apparently). Similarly Harada wants signatures for Soul Calibur 5.