I don't see why laroche would take less than 4 years. He is the top infielder on the market and the second best lefty hitter. Someone will overpay for him. Pirates, Mariners, and Red Sox all strike me as teams that would be a good fit.
I definitely think that teams will offer him an "over-market" contract. My question is if Laroche will give the Nats a home town discount to stay with a contender.
Laroche is nearing the end of his career and the Nats are his best choice if he wants a ring. All the big spenders that will compete in the next 2-3 years have first base locked down.