The sleep function is the closest thing to what you are thinking of, but it is not exactly what you would need. This sort of auto-sensing power on/off control is common on subwoofers and appears on some power amps (including Outlaw's M200 monoblocks), but it has not been implemented on a receiver or processor that I'm aware of. One problem that occurs to me in including a feature like this would probably be determining what counts as "no signal". Do you count an inactive audio input, or inactive audio and video? Do you only monitor the active input, or do you monitor all inputs? It would get pretty tricky in a hurry, be very dependent on how source devices behave, and might not be very widely used.

Rather than simply say "no", however, I can offer an option that might suit your needs well: remote macros. I've been using a pair of macros to turn the TV, cable box, and 950 on and off with a single command ever since I got my 950, and it is something that the rest of the family is very fond of. You can set up a macro on the M1 button (for example) to turn the TV on, switch the 950 to the appropriate input (which will also turn the 950 on), and set the remote to control the appropriate device (TV, CBL, SAT, or whatever). Likewise, you can set up a macro on M2 to turn the TV and 950 off when you're done.