To me, the emphasis on 'FREE', in combination with the word Final suggests they are likely weighing their options, particularly with the currently imposed restrictions causing problems.
I question why Firaxis would end Civ VI now, with it's established player base, plus room for improvement & additional content, in order to take the time necessary to develop Civ VII (or some other title), as this would basically remove all competition to Humankind (& Old World), clearing a path for them to become dominant over the genre for some time. It may be that, due to engine and design limitations, Civilization VI cannot continue further, which is an unfortunate coincidence if so, or clever observation and timing on the part of the competition.
Are they admitting [temporary] defeat against Humankind and in tactical retreat, to wait and see?
Or are they prepared to devote a splinter team to continue development, saving the best paid content for last, in order to remain relevant and further revenue?
In the case of the former, a Civilization VII would have to be an altogether better game than both Civ VI and Humankind, so it suggests quite some time is required to improve the fundamental concept and implementation, in which time risk increases as some market share is lost, and other entries have already released expansions. Otherwise, if Civ VII is rushed to early release, complaints about vanilla V and VI will snowball, and darker times are indeed ahead for the series.
Although it's early, the question is, for those with both Humankind/ Old World and Civ VI, would you still buy an expansion/ pass for Civ VI, or opt to wait for an improved base game in the form of Civ VII?