Spence is to small for Canelo and to young to make 160 pounds anyway, he's going to have to grow into his natural weight class which should be, 160, in about a couple of years, so until then, we can only speculate and guess, using only limited viewings of Spence fighting at 147. But Spence is 5/10, fighting at 147, so he can put on about, 20 more pounds of lean muscle mass, just like Floyd did moving up in weight and Spence walks around at 170, so him making 160, should be no problem.
Canelo has to worry about Charlo and GGG and others instead of even thinking about Spence.
Spence has to worry about Crawford and Thurman and Garcia and Charlo"s brother and others before fighting Canelo.
There's probably a 90% chance Spence fights Canelo in 3 years at super welter weight when Spence moves up fighting for another belt and testing his ability to fight a fighter that fought at 160. By then Canelo should be roaming around at super welter weight and middle weight trying to win titles, or having one of the titles at 160, willing to meet Spence at super welter weight, until then, I can't say who wins this fight at 160, 154, because Spence just might turn into Terry Norris or Julian Jackson, Spence just gets hit to much, like a young Floyd and Terry Norris and Julian Jackson, but Floyd turned out just fine, but Terry and Julian, never learned proper defense.
This is my predictions involving Spence Jr"s career, Spence will clean out 147, not losing to anybody and then moving up to super welter weight cleaning out this division, then fighting Canelo at around middle weight and super welter weight, beating Canelo, then fighting at 160 winning titles and losing some fights, then moving up to super middle weight and winning titles and losing some fights.
So we will just have to wait for the Spence Jr vs Canelo Alvarez fight to happen in about 3 years, like we eventually had the Floyd vs Oscar fight. This seems to always happen eventually with great fighters anyway, when one great already moved up and was king, then a young great moves up and takes his crown, more then likely this will happen anyway, we fans just have to wait for this mega fight to finally happen.