William Petersen on 'CSI' (for ONO?)

Hey, did you catch "CSI?" Good episode, but best of all: Bill Petersen, the mastermind of this CBS chestnut who has been off the series for two long years, oh, how we miss him, had a cameo. Marlee Matlin starred, too. Also good. He was talking to his mom and Sara Sidle (Jorja Fox) via Skype. His mom is deaf; he knows sign language. As soon as a clip is available, I will post. Question is, will he be doing more episodes? Or was this for one night only. I suspect more.