I considered it, but it's kinda far beyond the scope of the game so it wasn't planned to happen, and wouldn't fit so well in the architecture now.
Certainly plenty more maps/areas I'd like to add underground, but no further plans for the surface. Is fun to imagine though. Actually:
My original plan for the end segment on the surface was to have you fight your way past some guards to the Tor, but just that would've been a huge amount of work to get operational as I envisioned it, so I then switched to considering having that sequence but just have it be entirely automated, but even that was going to be too complicated, so I settled for the simple movement animation that we got. At least it makes sense thematically, anyway :)