I think Pochettino will leave Spurs within two seasons, but not because of Spurs itself. I think he will grow very tired of the level of competition in the league, where certain clubs can throw cash at everything and undermine what he is trying to achieve in London. In the end, he might feel that he has done the maximum effort and achieved absolutely nothing for it. Football is about winning trophies and it is extremely dufficult to do so in England - where you have Man City and Chelsea backed by rich owners, as well as United with enormous financial power.
Imagine Chelsea doing worse than Spurs this year, then suddenly they spend 250M on players including snatching two players Pochettino would have wanted, or City or United for that matter. Of course his motivation is going to go down, especially when he knows the same work would have yielded a trophy at another club or in another country.
And please cut the crap about the new stadium! Who cares about a new stadium? It’s still not going to be close to being the biggest in the world, or England, or even London! Like all new stadiums it’s going to be a corporate arena designed to make money - Pochettino wouldn’t give a shit - after this year they will be playing for less people anyway, so he’s already seen big, new and shiny. Wembley too have the Spurs-logo on it this year - and it still doesn’t feel like home.