In my opinion that makes little sense. They could not market upscaling as HD content successfully. In fact that would border on fraud. No one would want to buy it or watch it as it would be no improvement over SD. If they want to continue to generate income from the old shows they will have to remaster them all eventually or let them fade into obscurity. And that would be a great mistake as many people, not just Trekkies by the way, still love watching these shows.