it would be nice to have some sort of estimate.
from this post
"They further revealed that tests had been done for a possible future Star Trek: The Next Generation - Remastered effort."
about it in 2006. [nothing new at the link]
Paramount Home Entertainment have done their 'tests' which probably included uprezzing the standard definition D2 masters as well as re-telecining a few rolls of original camera negative to see the quality in HD [as 4:3 framing with pillarbox]. That was in 2006.
The quality hasn't changed a whole lot since but they know the costs and the amount of work it would require including the # of effects shots per episode they would have to have Eden FX do in CGI and the costs involved.
Once Paramount/CBS sees how the sales of TOS-R on Blu-ray go it may help them make a decision as well as the new ratings for broadcast syndication in Autumn of TNG.