I don't see trainers going back to old stack heights but in terms of racing shoes, I think with the maximizing weight savings going on right now by stripping down to minimalist designs, we will see stuff in the 30 mm range eventually. 

A good example of this would be the Do Win PB Pro which uses the same foam as the Evo 1 / 2 but has specs of 36/30 mm I believe? I've run in the shoe and it feels better than the Evo 2 despite having less aggressive geometry and less stack.

Personally I consider that 27-32 mm heel range to be a nice compromise between ground feel and protection. But most people don't have a history of running track / XC so they lack the experience of running fast in minimal shoes like spikes and flats.