Ben is an average goalkeeper who needs to develop somewhere else. he will never ever be given a proper chance in our first team, hes older than de Gea and Sam Johnstone is already better than him, we also signed that serbian goalkeeper for almost 2mil so he must be something and pereira shows potential as well.. Amos leaving is win win situation, lindegaard will leave as well IMO not sure if this season but he doesnt want to be a always backup goalkeeper and has quality to play for at least midtable premierleague team I rate him quite a lot he was just unlucky that David is here cost a lot of many and has got a higher potential obviously...What makes you think Amos will leave?
so in the future its 1)de Gea 2) Johnstone 3)one of the two Perreira/Vanja. Not sure about the next year tho, Johnstone can go out on loan to gain even more experience and Amos will be again third choice keeper... Sam will benefit more from playing of course