I don't see Mario or Dareus leaving before 2016 season.
Urbik does not cost too much money. We have cap room. Also, at this point we have 3 options at back up Center. All 3 are Guards. Urbik, Legursky and Asper. Legursky is most likely getting cut as he is about the 6th or 7th option at Guard. Asper is slightly ahead of Legursky, but, more unproven and is on his 3 NFL and 2nd time with the Bills. So, Urbik is most likely starting at Guard this year unless someone out plays him at camp. And, regardless of him starting at Guard he is the 2nd option at Center.
TJ Graham and Pears are my first two picks to get cut. I think neither are big names and both from the old regime. IF Pears is out played by all three of these players OR at least two of these three players....Cyrus Kouandjio, Seantrel Henderson, and Chris Hairston. But, we need at least 3 tackles on the roster excluding the PS. So, Cordy Glenn and two of these make the roster.
To clarify 3 of these 5 need to be on the roster...Cordy Glenn, Cyrus Kouandjio, Seantrel Henderson, Chris Hairston, and Erik Pears. Possibly 4 of the 5.