I don't think it would have been any easier to swallow selling them last summer, in fact it would have been worse. And selling them with 2 years to go or selling them with a year to go, it's all the same really. There's also the fact that you can't actually force someone to leave.
What we really need to do is get ourselves in a situation where the majority of players will have no doubts about signing new deals. Making Petr Cech your only summer signing and losing out on the title to Leicester City and then subsequently falling out of the top 4 is not the way to go about doing that.