Most groups don’t get stuck because they lack ideas. They get stuck because they hate the “fog”, that awkward middle space where nothing is clear yet.
So what to do when the fog rolls in during a futures session? My approach is to make ambiguity a shared, normal phase of the work. I ask the group to name it. We give it a time-box. We add a small experiment. We agree to lower the stakes.
The purpose is to let people try something before they can explain it perfectly.
For me, futures work often begins by giving people permission. We make it clear that people are allowed to be unsure, and still participate. In fact, sometimes the most interesting stuff lives in the unsure spaces.