Well, "Babylon Squared" also alludes to Babylon 5 being destroyed in the future (Sinclair's flash-forward to Garibaldi making a last stand) - I think there was a clear intention during the first season that B5 would be destroyed in combat during the run of the show.

And, of course, "War Without End" goes out of its way to explain those references, something I don't think would have happened if Ladira's vision had always been intended to refer to "Sleeping In Light".