If we trust the polls, pirates are in ~6%, the left is out with ~4% and the FDP is out with ~2%. (threshold 5%).
But of course pirates and left are still within the margin of error. And the left can hope that these results can change during the campaign.

Neither party, nor even the greens can hope to gain a constituency seat. 2010 only SPD and CDU gained constituency seats. Perhaps this time the greens succeed in one of the four cologne constituencies. But surely not pirates or left or FDP.

So a four party parliament: SPD - CDU - greens - pirates seems most plausible right now.