Johnson was the subject of a £9 million bid from the Latics just two weeks ago and it is thought that an improved offer of over £10 million has been enough to tempt Everton to sell.
Meanwhile, the club are expected to add Lee Cattermole to the playing staff early next week. The 20 year old combative midfielder has been for talks with the Latics after Middlesbrough accepted a £3.5 million offer for his services.