There will be no power boost for the LCI.
If the 2014 M5 got a power boost, then it would have more power than the more expensive 2014 M6 Gran Coupe. I don't see that happening. It's common sense.
At best they will offer a M Performance tune.
My own belief is that the M5 won't receive a power increase at all during the entire production run, unless it is tied to the release of an AWD model. Otherwise the car will have too much power. BMW cares too much about driveability.
2014 Porsche 911 Turbo S
2015 Mercedes-Benz C300 Sport 4MATIC