Not quite; the plan was always to go for five seasons, but the PTEN network closing up shop put season 5 at risk.

Sleeping In Light was always intended to be the finale; once season 5 got secured they shot another episode (which was also great) to act as season 4 finale.

The uncertainty with season 5 did play havoc with the pacing of the arcs. Season 4 did have to cover a lot of ground to get the most important arcs to close, so parts of it feel rushed, and vice versa the beginning of season 5 takes a while to get back to speed. Sigh.