I’ve been asking myself the same question lately, but in the context of having a Soul, Mukluk, fat front Jones and rigid Scandal 29er. The Jones can do everything the Soul does, but benefits from masses of grip up front, so my Soul has been sat in bits whilst I figure out what to do.
A 26″ FS would cover off rougher stuff where the limitations of the other frames becomes apparent and allow me to swap my fork and wheels over. I planned ahead when I bought my fork by getting a 120-150 TALAS, thinking the Rocket would be the eventual upgrade path, but that seems unlikely the way things have gone for Cotic, and I just can’t see me buying a new 26″ frame now. A Banshee Spitfire that could take both 26″ and 27.5″ appeals, not sure if 150 up front is enough though.