I think the question of "when" may be a little premature. The question should be "if" from what I've seen. Lots of bases are expensive, so I'm sure mgmt is not rushing to open a base when they can just keep doing what they are doing.
I finished recurrent last week and no mention of the DFW base was made.
However, in talking with two people whom I believe to be reliable, DFW ops will expand with 15 airplanes based at DFW. However, this will happen before there is a DFW crew base.
One of the people I talked with mentioned the 70-seaters will go to DFW because of the possible return to Mexico flying. With LE flaps and B model engines, that airplane will do well in places like Mexico City.