Dale Jr announced today that he will be leaving DEI at the end of the season, and here's my theory why...

DEI and Yates are merging. Since Yates has an established engine program with the Roush-Yates engines, DEI will be switching to Ford next year.
Dale Jr has said a number of times he will not drive a Ford, that's why terms could not have been met between him and DEI and is the reason why he will be leaving DEI.

Dale will obviously go with Childress, since RCR plans on another team for next year anyway. They'll take Dale Jr and his sponsor, Bud. DEI may let the number 8 go along with Dale Jr, out of good will.
No chance of Dale Jr going to Hendricks, their stable is already full, but what a team that would have been. Jeff Gordon, Jimmie Johnson, Dale Jr.
NASCAR's "Dream Team".

I'm not sure what all is envolved with the DEI/Yates merger, but with Greg Biffles contract up at years end and Roush dropping the #16 team anyways (due to NASCAR's "4 teams under one roof" rule) I see Biffle as being the number 1 candidate to fill the void at DEI/Yates.