Watford today never sat back, Newcastle might try and make it difficult like Norwich did, no absolute guarantees that Leicester will definitely win.
Having not watched it, I'm surprised and a little angry to hear you say that Watford didn't sit back. Leicester are top because they're lethal on the counter and a hard working team that defend well. The way to combat that is to sit back and deny them space like Norwich did. Watford are not a team with enough quality to try and attack them.
It's little wonder they're top when teams still go at them expecting to match them and just play to Leicester's strengths. That's another reason they're top. At first they were an unknown quantity, and even now, teams are only just establishing a game plan to stop them, whilst we've been playing against parked buses all season.