Changes to bowl lineups are coming for 2020 and beyond according to Stadium's sources. Not sure what the affect will be on the Sun Bowl but it looks like C-USA will have 7 bowl slots in the future. Some years the conference has less than that so I see that as a positive.
https://watchstadium.com/news/college-football-bowl-game-changes-to-begin-in-2020-03-05-2019/
"Starting with the new bowl cycle in 2020, here are the guaranteed minimum bowl tie-ins per conference (not including any teams that appear in the College Football Playoff):
ACC, SEC – 11
Big Ten – 9
Pac-12 – 8
Big 12 – 7
American – 7
Conference USA – 7
Mid-American – 6
Mountain West – 6
Sun Belt – 5
Army & BYU each can secure its own automatic bowl tie-in, but the remaining independents (Liberty, UMass and New Mexico State) must hope for an at-large spot from a conference that can’t fill all of its allotments in a specific year. Notre Dame remains part of the ACC’s bowl lineup if the Irish don’t qualify for a College Football Playoff or New Year’s 6 Bowl berth."
https://watchstadium.com/news/college-football-bowl-game-changes-to-begin-in-2020-03-05-2019/
"Starting with the new bowl cycle in 2020, here are the guaranteed minimum bowl tie-ins per conference (not including any teams that appear in the College Football Playoff):
ACC, SEC – 11
Big Ten – 9
Pac-12 – 8
Big 12 – 7
American – 7
Conference USA – 7
Mid-American – 6
Mountain West – 6
Sun Belt – 5
Army & BYU each can secure its own automatic bowl tie-in, but the remaining independents (Liberty, UMass and New Mexico State) must hope for an at-large spot from a conference that can’t fill all of its allotments in a specific year. Notre Dame remains part of the ACC’s bowl lineup if the Irish don’t qualify for a College Football Playoff or New Year’s 6 Bowl berth."