I do think a futuristic setting would be really interesting, especially in a way where technology has surpassed bending as a combat form in a military sense. It takes many years of training to master a martial art and 5 minutes to learn someone to shoot an AK-47. In a futuristic world bending would still exist but be more of relic of the past, practised as a sport or a form of martial arts show/entertainment a bit like shaolin monks of today. Bending would be far more uncommon then it was during ATLA and The legend of Korra because it holds less of a meaning and is a tradition that is in great decline. The story could revolve around a group of benders who somehow got involved in something greater and needs to use their art to resolve it and empower the traditions of old.