Since BYU has never been ranked once in the CFP polls. We do know that our best season (9-3 in 2015) wasn't good enough to even crack the top 25.
We also know that every three years (such as 2019), there is only one at-large berth available for a NY6 game. The last time this happened was in 2016 when #8 Wisconsin took the spot. I'm not sure if the Cotton Bowl is required to take the highest ranked team or if they can take the sexiest team which can bring them the most fans, TV eyes, etc.
We also know that one of the G5 champions will get a Cotton Bowl bid (and it most likely will come from the AAC or possibly the MWC/MAC).