Kone, McAleny, Valencia (loan spell), Browning - contracts all finish this summer
Jagielka, Lennon, Mirallas, Pennington, Barry, Gibson, Robles, Barkley, Deulofeu - contracts all expire in 2018
Oviedo, Rodriguez, (2019)
Cleverley, McCarthy, Mori, Niasse all expire 2020
The 4 whose contracts finish this summer - 3 of those are nailed on to leave, with only Browning the possible excpetion (although have to say likely he will leave due to the amount of young lads we have coming through in the same position)
The ones expiring next summer - this window will be the last one where any value on them will remain 'relatively' intact, soon as they enter the last year of the deal then there value plummets - Barry obviously won't go anywhere and will retire here most likely, the rest could all possibly be moved on (hopefully not Barkley and we get him a new contract) - of that lot, Jageilka, Mirallas, Lennon, Deulofeu are all 'sellable' players without a huige amount of trouble and would find buyers. Pennington, Gibson, Robles, - likely either have to give them a free (paying off part of their contracts) or leave them to rot in the reserves for a season and a half as no one will realistically come calling for them and pay money.
Ones on longer deals, - Ovideo, Cleverley, Niasse, someone might be stupid enough to pay us for them, else we will have to loan them out - none of them will realistically feature much again for the team.
McCarthy, Mori, both good likeihoods of moving on within the next 6 months - both would bring in a good fee and would be 'easily' sellable
Out of the entire lot of those players - the only ones i can see this time next year still being at Everton AND featuring in the first team squad would be Barkley (possibly Mori)