The 21-year-old has already been the subject of numerous offers from the London club, with their last rebuffed bid coming in at around £30m.
Although Everton have maintained publically that their man is not for sale, Gray told talkSPORT that he cannot see any other outcome than Stones moving to Stamford Bridge:
“Chelsea see John Stones as the ideal replacement for John Terry, without a shadow of doubt, so it is a case of how much he is worth to Chelsea.
“I think Everton know that now. That is maybe why Chelsea will have to up the ante a bit but I do think sometime this month Chelsea will take John Stones and make him their player.
“I would be amazed if, at the end of August, John Stones is still at Everton.
“Everton are not at the stage now where they can look at everything and say we don’t have to sell any of our players. We do, it is as simple as that, and I think it will happen.”
Everton have been linked with replacements such as Celtic’s Virgil van Dijk, and Gray went on to say that, should a worthy successor be brought in, his old side could become stronger as a result of selling Stones:
“It is still a work in progress for Roberto Martinez and if the bid is £35m to £40m I don’t think Everton can turn that down.
“I would be very surprised if Roberto hasn’t got something set up should the deal happen so he is ready to move when it does – and I think he will be ready.
“It’s sad but if £30m to £40m comes in and Roberto spends it well, there is absolutely no reason why Everton can’t benefit from it.”