Yes, it is possible that if you place these calf roping horses on LubriSyn that they may need fewer or no more hock injections. A lot of this will depend on the amount of work you place on them and other factors like: the number of times they are run at ropings, the amount of practice runs they need at home, the amount of arthritis in their hocks and their conformation.
As far as the coffin joint is concerned, the fragment in the joint is of some concern. In addition the amount of changes in the joint associated with the chip fragment will also give an indication of just how well you should expect this joint to prove by adding LubriSyn. Furthermore, the number of times the joint has required injections will also help in making a good prognostic call on results that you should see. Please supply some more information and I will help any way that I can.