If it doesn't increase the licensing fees, then what's the motive for CBS?
Simply to continue selling Trek (in HD) as a cheap rerun, whereas the market for SD reruns will wither away.
If it is truly intended to be a "cheap rerun" then the results will not even remotely resemble the results of TOS-R or even TNG-R.
Cheap does not mean pulling the film elements from a salt mine.
Cheap does not mean rescanning said film elements.
Cheap does not mean recompiling the visual effects from either the original film elements or the digital files which may or may not actually be viable in HD.
Cheap does not mean anything remotely resembling what we got with the TNG project.
The closest comparison would be the Doctor Who series 1-4 Blu-rays, which were upscales from the SD source, but those had the benefit of the larger PAL source resolution (576 vs 480, if I recall correctly) that was easier to upscale. They even sold Blu-rays that way, and they're close! But they don't compare to the HD transfers of everything else.
Neither will a "cheap rerun" version of DS9 or Voyager in upscaled "HD".