Regarding the other chapters, initially SQ 42 was supposed to be released in 3 chapters, but initial backers were supposed to get those 3 chapters (or at least a free second chapter) ... so it was more a question of release in 3 differents steps ...
Now we didn't get news on the release since 3 or 4 years.... so things may have evolved ... but regarding the evolution of pricing, it is fair to assume that new players will have to pay for each chapter separately.
And what is called a chapter may be a little bit reducting : the actual first chapter is something like 28 missions ... so a lot more than any actual AAA solo games
Yes TF2 is a very good example of a community supporting a game for more than a decade, a few others game have succeeded in this way, so this business model would be a good alternative ... and it is already pretty much the case with the selling of individual ship as you would pay for individual tank, plane or ship in warthunder or world of tank/ship/plane.