I'll copy/paste what I wrote to someone who asked if the game is abandoned:
Never, my friend. Polarity is still ongoing. That said, Chapter 5 is the biggest chapter yet: it's 30% larger than CH4 and has a ton of animations and other aspects that make its development time a little longer than normal.
It's the finale of the first half of the game, however, so it's going to be a good one/worth the wait.