TNG was created for a 525-line interlaced resolution master. All departments knew the limits of the resolution at the time of production and could hide visual problems due to this.
TOS was retelecined to HD at 1080/24p . TNG episodes are NOT going to be telecined at 4K. Only A-list feature films are given the 4K full treatment since 2004's Spiderman 2 which was the first all-4K pipeline Hollywood feature release. Scanning a TV series at 4K and downsampling to 2K for a Blu-ray release is really not worth the additional cost for a 22-year old TV show. It is not going to be projected on a 80-foot screen for 99 percent of the audience to see additional detail. I find it highly unlikely that 1960s-2005 Star Trek TV series would be sold higher than 1080 resolution in any future consumer video format.
If a new TV series in 2012 were shot on a 4K digital camera that is a different story for future releases of TV series. At that resolution it gets very difficult to hide makeup edges of appliances/layers for live-action aliens.
But the resolutions of screens increase all the time. Smaller screens today have much larger resolutions than bigger ones just a few years ago. Also I could quite easily see projectors and larger screens for home media systems becoming fashonable once they get cheap enough. So I guess there is quite a bit of potential for a home market beyond 1080p. It most certainly wont stop there. Technology will continue to improve. In 10 years people will look down on that format as we to today on DVD, which 10 years ago everybody was dazzeld by.