The Toffees have assembled one of the most talented, young squads in the Premier League, but there are doubts over many of their key asset’s futures ahead of the summer transfer window.
The likes of Romelu Lukaku, John Stones and Ross Barkley are likely to be in demand in the summer, and Everton may not be able to offer them European football.
The Merseyside club have badly unperformed this season, and Keys fears that there could be a mass exodus at Goodison Park over the summer.
“I sense there's some big decisions to be made at Everton pretty soon,” he said. “What a wasted season. Roberto Martinez has assembled their best Premier League squad ever, but he seems incapable of getting a performance out of them. They were poor at United. I know there's another cup semi-final to come but 12th? Not good enough.
“I'll tell you now, the squad won't be this good next season. I don't care about all the tough talk, if Lukaku wants to leave - and he does - then he will.
"Stones will also go this summer, but I think most Evertonians would encourage that right now. I wonder if his value has slipped from the near £40m Chelsea were offering last summer? I said then 'sell'. They should've done. What have they actually achieved by not doing so?”
Everton will be determined to keep hold of their key players in the summer, but they could be fighting a losing battle.
Although the Toffees have attracted new investment, and now have the financial power to compete with most clubs in England, Romelu Lukaku has already suggested that he could move on in the coming months.
Lukaku said to the Daily Mirror that he wanted to play Champions League football, and Real Madrid are one of the teams who are believed to be ready to pounce to sign the 22-year-old forward (The Sun).