I would let Rabiot go now just so we don't risk losing out on SMS/Frattesi, time is everything, we cannot sit in hope that Rabiot gives his answer, and should he reject it, our potential plans have already been blocked. Besides whats the point signing him for 1 year and he goes for free next year anyways. We may never have a better chance to bolster the midfield with someone like SMS.
I just dont get why Rabiot needs so much time to think about it, for me, you either want to play for Juve or you dont, no 2 ways about it.