Yes renew now because although you do not plan on exiting the airport, sometimes things happen beyond your control and you are forced to exit the airport. It has happened to people many times including here. Your question implies you do have the option to renew, exercise it now and eliminate the risk, however minuscule.
How much do you save by waiting till five months before renewing? If you have a passport normally valid for 10 years, that's less than 5% savings. For a $80 passport, that is $4 of savings. Is it worth getting denied boarding, or any conceivable hassle etc? The numbers I use are only assumptions however you get the idea, its not worth waiting.