It does not make a lot of sense for MacDonald to take this fight, other than a healthy pay day. I can understand him staying pat for a bit. Much like Carlos Condit after he defeated Diaz at UFC 143 and then waiting for the big money unification fight with GSP fight later that year.
Johny Hendricks makes a lot of sense as both he and Brown lost to Lawler in their most recent fights, but I can't see him taking the fight on six weeks notice. Especially after his grueling last fight, and the weight he carries between training camps. Colorado altitude could make him gunshy on taking the fight.
If Condit is not ready to go, and from most recent reports he indicated that he hoped to return in March/April, then a rematch with Kim probably makes the most sense for Brown. Both Brown and Kim are coming off losses, and have a history/story line with a controversial decision several years ago (UFC 88!).