It costs UFC a lot of money when the big draws like GSP or lesnar can't fight.
Their second best option is Anderson Silva and Jon Jones. With Jones they can really build a ppv star, so they wan't to keep him busy.
Rashad is known to get injured in training, a lot. They therefore can't schedule him long beforehand for a titlefight as theres a high risk of having to replace / scrap the fight all together.
It's unfortunate, because Rashad vs Jones is one of the most appealing fights out there both from a fighting standpoint and from a business standpoint.
Thats the fight the UFC wants, but i guess everything must lineup perfectly for it to become a reality.
I hope Rashad gets the next shot, but i think the UFC is waiting it out a little more before deciding.