They would be stupid if they did. They get mortar shelled from the settlements is why they took over them in the first place.
They didn't "take them over" the settlements are newly built civilian towns and villages. They don't increase security, they require huge numbers of Israeli troops to guard them, at great cost, both in lives and money. (to both sides)
The driving force behind the settlements are religous Jews who believe it is their God given right (and duty) to live in the West Bank. They call it "redeeming" the land.
There's an interesting fact about Palestinian home made motars. They haven't killed any Israelis.
Suicide bombs have killed hundreds.
Israel has a peacefull border with every Arab country it's made peace with, and a relatively peacefull border with the others (Hezbollah and Syria)(yes Hortlund I know Hezbollah isn't a country)
It continues to intermingle it's soldiers and civilians with the Palestinians, whilst denying them citizenship, in Israel or a country of their own. The Palestinians have been subject to land siezures, deportation, and Israeli military law for 35 years.
There's never been a case of a population being ethnicaly cleansed that went peacefully, and this was never going to be the first.