I honestly feel that outside of Bonanza, Gunsmoke, the completion of Rawhide, and MAYBE more Happy Days, PJ, and Hillbillies that CBS is probably winding down the pre 80's stuff. We have heard about re-mastering of Miss Brooks and Chapparal, but that could mean nothing, so what realistically...
The question now becomes, where do they go from now with these series. As far as I can see, there are four main possibilities.
1) Back to the shelf.
2) Widespread release.
3) MOD (not likely)
4) Something like an exclusive yearly holiday release at Wal - Mart.
The only good bet right now is...
Future seasons of Cannon would be hard to predict since the 3 already released weren't transferred to HD, so most likely, if season 4 was in the works, we wouldn't see nothing here anyway.
I did a quick check on some titles that interested me and no updates on Hillbillies, PJ, Happy Days, Barnaby Jones, or Cannon. Don't know what they updated.