You kid, but I could see them going for that. Obviously we'd have to sweeten the deal considering Sterling's contract situation.
They must know they can't afford Sterling's wages unless they offload Kane or Son. Son will never be worth more than he is right now.
If they could swap Son for Sterling and a bit of cash, they'd be replacing a world class winger for a slightly younger, English world class winger - who also has a great understanding with Kane.
The only thing stopping them is the fact that Sterling wouldn't want to go to Spurs. Because nobody wants to go to Spurs.