Well, if the (T20) TNS is for the Gateway (?) sector in 1000, then it could be forward compatible with the other classic (or GURPS variant) TNS timelines.
I mean, since you know what officially happens around 1100+, you can take that into account in the new TNS entries.
Sure, the adventures that QLI publishes* might cause changes depending on how individual groups play them, but that is true of adventures/campaigns published for any of the other official Traveller incarnations.
* I do NOT mean to imply in any way, form, or manner that QLI plans to publish material that "invalidates" official, canon material that occurs later in the timeline. However, each of us make the Traveller background our own in our games, and we can easily (especially with some players
) have our campaigns diverge form the official, canon, version.