I heard a rumour that the Spartan ops production has been handed over to machinima.
Also another rumour, Spartan ops is scheduled to come out near halo 5's (if there is another) release and a 10-20 episode season with 10-30 min long episodes weekly that explain more about the origins of halo and the construction and the actual mission of infinity and the halo rings.
These are rumours though but I doubt they are true as its a lot of effort to make 30 minute animations.