The writing was on the wall for him when the club didn't take up the option of a extra year and allowed him to go into the final 6 months of his contract, which allows him to talk to other clubs. But under Woodward I feel he would've signed a new contract a long time ago.
I think it's a matter of when he leaves and not if he leaves. I think the club possibly have a younger keeper in mind and want to retain DDG to ease the new keeper in. Now it remains to be seen if DDG accepts reduced terms or we do what Milan did with Donnarumma and sign a younger keeper with the potential to provide the pro-activity on and off the ball, which has not been seen at United for a long time.
I've always consistently said that DDG isn't saving us but rather he's a major contributor towards the team not evolving into a proactive, attacking team. I think he's been very fortunate we appointed managers post Fergie who were more reactive than proactive. Because if someone like Guardiola had turned up post Fergie, like many fans wanted, then DDG's career at United would've been very short lived due to what Guardiola expects from his keeper both in the build up and in defensive transition via sweeping.