The thing I really like about this future-set episode, over last season's finale, is that you really get a sense that this is what's to come. With the S3 finale, that future scenario was pretty much entirely erased by the episode's end. With this, not so much. Nothing happened that would cause our present timeline to avoid any of what happens down the road. It's like the writers are setting up this perfect swan song next season with the Observer threat. And please, Fox Gods, grant us that fifth season.