There will be some new faces in mainline later this year, but I'm afriad that most of the positions that will be filled already have names penciled in for them. As mentioned before, these will be in the form of baby and regional guys and those that are left from their 'cadets' from 2001.
If you are an outsider trying to get in - then I wouldn't hold your breath. IF mainline advertise, it will be for very few positions that won't start until the end of summer. I wouldn't hold out for mainline - keep your options open.