1) will the .45LC barrel be able to handle the .454 pressure?
I would think so, if a rebored .308 barrel can handle it, I would think the .45C should be able to, but we'll have to wait and see and get a professional opinion on that.
2) will the new barrel come ready for .410's as well? If so, is any chamber modification necessary to fire .454's? (I thought the only difference between the .45 and .454 was chamber length, and the .410 should be much longer than either.)
So far as we know, it will be a .45C barrel, not a .45C/.410 combo barrel like on the Survivor.
Tim