I think most people wouldn't be very upset if the constant HD stream from a Mars rover is 5-15 minutes delayed.
The real issue is the cost, bandwidth and infrastructure in place to make that happen. Scientists would rather want to use bandwidth, power, launch mass and real-estate on the rovers for science instruments - orbiters around Mars which relays data must be upgraded to handle more bandwidth, the DSN on Earth that receives the data can't be dedicated fulltime to one data stream, etc.
(That said, the new laser communication systems NASA is experimenting is pretty awesome, and will greatly improve bandwidth for space missions)
As I understand it the satellites used as relays are in quite low orbits which limit the amount of time available for rovers to upload. A communication satellite in areosynchronous orbit or at a lagrange point could give more upload time. But presumably that would require more capable transmitters on the rover.
