Well, yes, we do want to see
Well, yes, we do want to see proof. However the way battery improvements work there are occasional huge leaps in capability. The leap from lead-acid to NiMH and NiCD was a 2x improvement, and the leap to Lithium-ion was a 4x improvement over lead. For both those advances there was not an iterative 5% improvement every year, but a dramatic jump, though it did take over 20 years from when lithium batteries were first developed for them to become common in automobiles.