I think now is the ideal time toe Hernandez to leave, from from the perspective of both parties, so I do hope a deal comes to fruition from an opposition club this summer.
On Hernandez's side; his United career has been uncertain for the past two seasons due to game-time and considering van Gaal favours just the one forward and is always inclined to give youth (Wilson & Welbeck) an opportunity, it'll significantly reduce Hernandez's starts even further. He's 25 now and needs to be playing regular football, if only for his country and their prospects.
From the club side; Hernandez has hit an age whereby I don't think we will see his market value increase beyond what it currently would be. More specifically, he is a limited player with few quality attributes in his favour. One of those is pace and it is only natural to think that will regress, so he has only finishing and movement really in his favour then. If we cash in now, we could recieve £15M if we're lucky with Atletico being potential suitors. Additionally, his presence is to the detriment of Welbeck and Wilson's development here. If Hernandez was to leave, simply in order to give those two more first-team opportunities, so be it.
I appreciate everything he's done for us and he was an excellent signing, but if we make a significant - even a reasonable profit - it's an easy decision for me.