I know I'm a little late in my answer but still, I will chime in.
First I will say that, both at 26, I will still consider Djokovic and Murray as in their young prime. At 27, Nadal, even if his injuries will most likely still follow him until he retires, can be quite effective.
I do however understand your point. Raonic has now change his coach and hopefully will achieve his potential. Getting into a final of a Master 1000 tournament last week in mtl is a good start, even if he didn't make it as easy as it could have been. Granted he got his ass whooped in final against Nadal but still it's a good start. He will need to learn how to finish his games to go to the next step.
In Canada, I would say that Vasek Pospisil could become better than Raonic in not that long. He has a serve that is almost as powerful, but he's more intelligent and is quicker on his feet.
I do agree with you, Benoit Paire and Janowicz are to be looked at.. I will finally say that we shouldn't ignore Del Potro, who's still young enough.