Yeah, Season 4 is acknowledged for compressing a lot of the story that would have been Season 5 in the original plan. The series finale ("Sleeping in Light") was even shot as a part of Season 4 and delayed once Season 5 was picked up to keep it the series finale. The epilogue it tells spins out enough past the show that it mostly isn't that noticeable, but the big tell is a brief appearance of Ivanova rather than Lochley, which doesn't really break the episode because of the out-of-order storytelling of the whole episode and the glimpses of the crew are "timeless" flashbacks, but it is interesting.

IIRC, this was because there was significant uncertainty about whether the network exec's would cancel the show after season 4, so JMS reworked things so that 4 wouldn't end on an open-ended cliffhanger if that were to have happened.

In the end, season 5 was given the go-ahead, and so now season 4 seems rushed needlessly.