I'd like to see the Flintlock season be left alone too, however, I think the writing is on the wall...
It overlaps with "Extended Firearms" season in the SRAs, in which shotguns and inlines are allowed currently.
The flintlock season has historically been viewed as a bit of a "non-factor" in terms of harvest/management goal impact... meaning it was never viewed as a "necessity" to reach harvest targets, or much of an issue cutting into allocations or lengths of Archery or Rifle seasons... It was and is a "boon" to the traditionalist or "primitive" hunter.
If hunter numbers were to dip low enough, at some future point, and some projections indicate they very well could, it might become necessary to increase harvests in the "late" seasons after Christmas, and one way to do that is to open up the list of lawful arms, hoping to encourage wider participation.
But before that happens, I believe we'll see a lengthened Rifle season with higher allocations, and probably an increase beyond the current 3 antlerless tags/hunter limit (non-SRA)...
But I can't discount the possibility of it coming to pass that other firearms beyond flintlocks get authorized outside the SRAs, for some or all of the season.
I don't view this as a "line in the sand" personally, I'll still walk the flintlock in January if I have a tag or two left by then. And, frankly, there's not many guys in the woods then anyway, even in the SRA area I hunt from time to time.