Extending Sheard is likely in their better interests, particularly since he has a 7m dollar cap hit this year. They certainly aren't going to pay that kind of money to Sheard, Jones, and Ninkovich. That would be about 20m dollars worth of cap hits.
The fact that they could save 7.8 m dollars by trading Jones a year before he's very likely to leave may be worth consideration, especially with other areas of need, limited cap room, 3 recent DE additions, and the lack of a first round pick. That's not even bringing up the situations of Hightower and Collins.
There's also no guarantee that we'll get back a 3rd round comp pick yet again. He could get hurt next year, be suspended, fail a test, or just have a mediocre year. I'm sure the fans of CLE thought they'd get a 3rd round pick for Sheard too, until he became injured and his play dropped.