That last conversation between Ivanova and Sheridan is heartbreaking, but not as heartbreaking as what comes next
Man, I just went through this. I watched Sleeping in Light instead of the actual last episode of S4 because I think it works better that way and holy shit, I cried so much. Again.
That was the original broadcast plan, it was meant to be the season 4 finale and series finale. But then someone thought it would be a good idea to have a fifth season despite the four season arc JMS has written (Was it TNT? I think so). Sleeping in Light had been filmed a year before it actually ended up airing.