Nice exercise! Even though I usualy hate the 10 year looks
But here goes.
Raonic may get into the top 2 and have won a slam or two if he stays healthy, gets back into form, and the big 4 retire. Of course there is also the possibility we have seen his best and he's on his way down, I truly hope this is not the case though.
Pospisil I think makes a return the top 50, and maybe nicks a 250 so he can at least have one tour level title, but I think he may end up focusing on doubles as he gets older and becomes a Nestor-type ageless doubles player.
Polansky gets close to but I don't think breaks into the top 100. He got so close to reaching a new career high these past few months, getting to 123, when his career high is 122.
Schnur continues to rise, should likely break into the top 200 in the next few months, but I'm not sure if he goes much further. He might pick up a challenger title. I'll give him a CH of 125.
Auger-Aliassime and Shapovalov could both be a top 10 talent, and possibly even give us two top 10 players at the same time for the first time in Canadian tennis history. The could also both be potential #1s and multi-slam winners. CH ~1-7
Sigoiun could be like Pospisil, peaks a bit here and there and get into the top 30, or he could be like Polansky, success on the Challenger and Futures tour but never quite breaking the top 100 or seeing success at the main tour level. CH ~70-120
Monette could be the same way as Sigouin. He's really hard to gauge right now as he seems to have come out of nowhere and had some decent early results reaching a couple of Futures QFs and a Final. If he continues that success and grabs a couple of futures titles he could move into the Challenger tour by this time next year. CH ~70-120
By the end of I think this would be the overall career 'rankings' of how these Canadians turn out
I tried to weigh conservatism with potential.