To me it would make sense to see where we are come January. If we have a realistic shout of the playoffs, and Bagan and/or Martin aren't showing enough consistency yet at left back then by all means bring Cunningham or Bennett back in.
If we are looking consigned to mid-table obscurity, then that would seem to be the ideal time to bring the youngsters through. They are both out of contract in the summer, and probably on large wages for us, both having been with us in the premier league.
If we could get one of them up to first team level and the other a capable understudy then that would be ideal as it's be a huge chunk off the wage bill, and one less position to have to address in the summer.