It could easily have happened if Lewis Cass had won the 1844 Election, not James K Polk. Cass was against further expansion westward. And it didn't take a genius to see that clear division between slave and free states would break down once the land was far enough west to discourage plantation agriculture. (In fact it just occurred to me that Stephen Long's characterizing of the territory west of the Missouri at Missouri as the Great American Desert in 1820 may have been designed to avert just this sort of breakdown, and sectional strife, 1820 also being the year of the Missouri Compromise).
Brigham Young's initial attempt to expand Deseret into the Snake River amd Lemhi Valley can be seen in this context (though Bark Beetle can clarify this).
Cass, with only minor prodding from Senators fearful of upsetting the balance of slave and free states in the Senate could have held off calls for US annexation of Texas. If need be, Texas, Deseret and California could become allied states with the US, linked in a mutual defense treaty without annexation and therefore without congressional representation or interference of any kind in state policies.