With no team forcing Atlanta to pay big money to Smith (I still don't understand why the Warriors don't go after him, or why the Clippers would prefer Camby to taking a stab at Smith, who's much younger and more athletic, doesn't have injury issues, blocks as many shots, and doesn't play the same position as another young Clipper, Kaman), it's very possible Smith only takes a one year qualifying offer from Atlanta for this season. The risk is huge for Atlanta, then, that Smith becomes an unrestricted free agent next year and bolts for whomever will pay him. In that case, they may want to hold on to Childress at the MLE since there will be more playing time.
But I'm still not so sure. I really think the MLE for 5 years may be enough - the Hawks' ownership is a mess, they don't want to take on long term deals and they may not see any reason to pay the full MLE for Childress to be the Sixth Man on a very mediocre team. In that case, we could get him, since it is worth the full MLE to get a bona fide Sixth Man on a championship contender, especially a Sixth Man who's in his early to mid 20s, not early 30s.