Terra will definitely get more screen time later, but we can't promise an entire route just yet, given that we have a whole list of Overwatch-inspired characters that are still waiting for their time to shine. Still, we love Terra dearly, so she'll get content one way or another.
As for your progression problem, I can't say for sure, but I'm gonna look into it. There's a chance two different stories block each other. Let us know if you found a way to pass this particular roadblock and how, because that would help at pinpointing the cause. Also, have you also been playing other routes at the same time with Seraphina's story?