I have a my Rasplex Pi hitched up to my 2012 Panasonic Viera and everything works beautifully (well, it's a little juddery in the UI but it's only recently been put together). It's powered off the TV USB socket - lovely - and CEC works nicely too.
One thing though: I put the TV on standby and, after a handful of hours, the Pi turns the TV back on, switched to the Rasplex input. By itself!
Maybe it'll turn on the USB port while the TV is still in standby. The Pi will start if it gets some power via USB which will wake your TV afterwards...