They might even get the 5th, since if Baltimore loses to Cincy in Week 18, the Chargers and Ravens would be tied, but the Chargers would have the better conference record.
Not necessarily. if Jax wins next week against Houston, and Tennessee loses to Dallas, Jax would clinch the divsion, since even with a loss in Week 18 to Tennessee, they would still have a better conference record (head to head and divsion record would be identical). Therefore, it still could be Baltimore and Cincy on SNF in Week 18 (or some other teams too). [Corrected by @MasterStrategist]