I hate to be pedantic, but a “relaunch” for TOS or TNG in the same sense as was used with DS9 for Avatar in 2001 isn’t likely. Avatar represented a new beginning for Deep Space Nine fiction, a new jumping-on point for an ongoing story. Because DS9 fiction had been historically the lowest-selling Trek fiction, the publishing line was relaunched in an effort to bring new readers into the fold with a new marketing and storytelling emphasis, and that effort succeeded.
To use the term “relaunch” for TNG or TOS in the same way that it could be used with Avatar, we would have to see a situation where TNG and TOS books simply didn’t sell, Pocket took those two series off the schedule for a year, and when the series reemerged the books presented a very different style of storytelling than had been common previously in TNG or TOS fiction.
None of those three things are likely to happen. TOS and TNG perform well in the marketplace. TOS and TNG, while they might not dominate the schedule as they did a few years ago, see a good number of books published each year. And TOS and TNG have seen a number of different, unique storytelling styles in the past five years that have gone beyond what we’ve seen on television–Double Helix, New Earth, the Original Series novels, next year’s A Time To maxiseries. And beside those works, there have been self-contained, standalone novels in both series. In other words, TOS and TNG don’t need a relaunch, because TOS and TNG sell well and will very likely continue to sell well, telling both one-shot stories and multi-part sagas.
I’m not trying to pick a nit, but I’ve developed a clear aversion to the term “relaunch.” :/