Unless it's Matic himself who's trying to force his way out I'd refuse to sell him. Juve can fuck off for refusing to do business with us regarding Sandro and Man United can fuck off for a whole host of reasons.
Matic can stay and be and excellent rotational player. If we enter the season in 4 competitions with only Cesc, Bakayoko, and Kante we'd be dangerously short of bodies. Say Kante picks up a serious injury early in the season. What the hell would we do? If Kante or Cesc snapped an ankle in China or Singapore we'd enter the season with only 1 fit CM.
We keep Matic and we have the strongest midfield options in the PL.