Unless Fushimi gets much more actual screen time with both other MCs, I feel like she's gonna get dropped at some point.
Karasuma and Shijou are mutual, but no one actually feels mutual for Fushimi. Karasuma was mostly just infatuated with a pretty girl he didn't know, and she doesn't really seem to like him back that much. Shijou mostly only said yes to the throuple because she didn't want to fun good times to end, and to help karasuma get in with Fushimi.
Fushimi just doesn't contend very well. She feels like 'romance option 2' right now. She needs more development.