I’d be shocked if it was more than four years. Ideally for the Pats I’d bet they’re willing to go three years, four might be stretching it. I’d expect a front-loaded contract with lots of protection against injury and playtime incentives at the end of it.
From a realistic POV I’d expect the Pats to be aiming to give him around $15 million over the next two seasons guaranteed with the rest of the money and years easily dumpable. So even if it’s 4-years, $30 million, a big chunk will vest first, then the rest will require Welker stay healthy and productive.