There's 3 Acts tot he game, and for the most part the main story is over now. All 3 Nat paths are held on a waiting point which will pick up and finish with Mission 3 when we are ready to end the game. For now though, we've got a fair bit of side content and sex to add (plus code systems to clean up and early scene to update texts on) before we're ready to close out the game. The amount of time that's going to take will depend on how much side content from our list we end up including and how much of a runway we need to get our next project ready to v0.1 release, so we can't say for certain just how long is left.
To the secondary point, no, Lara isn't likely to be the next protagonist (she's done that already), but she will likely have more of a role to play in later projects than she did in this one. To make a long story short, years ago (before we were beWilder long ago) Lara was to be a protagonist of a follow up game, but most of that has been repackaged to a companion comic to support this game as it grew to be a bigger thing. That might be were you got that idea from? Maybe, maybe not, but she's not a leading contender for the next spot right now anyway, even though we will be doing more with her.
Hope that helps!