Given the signings then I expect a flat back 4 and I don't think DK even contemplates the 3 CB system.
So its a question of balance with either a 442, 433, 4132, 4141 or any other combination
Wedgbury appears to be the holding CM so we can either play 2 alongside him as a midfield 3 and then Mackreth, Holroyd and Boden up front or a more solid 442 with Holroyd & Boden up front and then maybe Mackreth on RM but that leaves us playing someone out of position on LM unless we go with Rutherford as well.
I cannot see DK starting with both Mackreth and Rutherford and expect this to be his usual sub policy.
I therefore expect to see 433 with Wedgbury, Kelly and Wright as the 3.