2015 is one thing, but do you think any of those guys will be ready to replace him at the end of 2013? We're talking about a rock who gives 200 innings of low-to-mid 3's ERA every single season despite pitching half his games at Fenway. Webster is the best of the bunch, and he probably needs more time.
They need to either hold onto him long enough to have a good 2014, sign him for reasonable money, or trade him for the best they can get. There is a tough balance, and I don't like many of the options.