It would depend on how Wisconsin, Utah, Washington, and BSU do.
If Wisconsin finishes top 2 in the BIG10, and one of the PAC12 teams finish top 2 in the PAC12 and BSU wins the MWC, there would be no doubt BYU would be in the top 4 and go to the playoffs.
If those teams all finish in the lower part of their conferences, then BYU would just get a BCS invite.
The idea that so many people answer this question negatively without stating how the teams BYU plays this year shows a true pessimistic attitude.