The window has pretty much closed, IMO. However, if they can somehow restock the SP while keeping the RP good there is room for this team to be competitive for the next year or so. However, it will require the team to once again hit on all cylinders and they are going to have to find a long term answer at 3B and teach Tank the strike zone. Whether Beckham can carry over his offensive success of the last 4-6 weeks of the season will remain to be seen also. He's still not that old nor is he that productive.
I can't see them tearing the whole thing down, but maybe Hahn sees things differently. I imagine one of the issues will be financial. I would bet the Sox have been running a loss the last few years (maybe not this year, but last year) and it's one reason KW has been kicked upstairs (if rumors are correct). If so the Sox maybe cutting payroll or at least not expanding it until they get that money back. However, I admit that's also just a gut feeling. I have nothing concrete to base it on.
Riding shotgun on the Sox bandwagon since before there was an Internet...