First, are either of $subject games represented at GenCon Indy?

Next, having never played either, are there any pick-up games in the works? I'd really like to learn more.

I only see a single seminar event relevant to Torchbearer. The publisher will have a booth.

I don't see Mouse Guard or the publisher in the exhibit hall (but it could be under a name I don't know—especially since they've had a presence in years past).

Typically Burning Wheel carries Mouse Guard, Torchbearer, and, well, Burning Wheel in their booth.  They are the publisher for the latter two titles and designed Mouse Guard.

I suspect these were played in the Games-on-Demand room in previous years, but it doesn't look like that's going to be a thing this year.

They used to do small demos in the booth for Burning Wheel.

You might want to try their forums at https://forums.burningwheel.com/