I didn't expect more than a season out of him in the first place, and while he has scored quite a few goals, he offers little besides that. In this day and age, it's hard to accommodate a striker who does nothing other than poke the ball into the net. The game has moved beyond that, you need strikers to contribute to the team's possession and press and the overall strategy. If the player scores a truly outrageous amount of goals, like Lewandowski or Benzema, then it can be feasible. Ronaldo didn't, he just stood out in a shit team. He didn't really score any more than you would expect of any reasonably good striker, but nobody else has been doing their job so we've relied on him.
If he does go, however, it really heightens the pressure to sign a replacement. As it stands, we have literally nobody else who can score reliably.