It's already been agreed to. The Red Sox will not back out of the deal if they can't sign to a extension today. I'm sure this was a window to see if it was possible to extend him now, but more to gauge how hard it will be to sign him over the next year. The window is not for the trade to be completed. It was a window granted to discuss a possible extension. I'm sure since everything else has passed and they feel like they can come to terms with Agon at some point in the near future, the deal will go through.
And if not guess what? I'll be right here rooting for whoever they put on the field. You can go jump off a bridge if you feel it necessary.