My wish:
MS should shift strategy and focus all available resources on making WP the single best platform for mobile/casual/social/cloud-supported/high-end gaming. I can think of nothing else that would resonate with enough consumers to boost WP from mediocre to acceptable market share.
Currently, MS' approach is to make it easier to port existing Android and iOS games to WP, which usually occurs as an afterthought. That won't sink WP, but that approach won't get WP anywhere either. WP needs some killer feature that is so obviously better, that it markets itself. MS' current focus is important too, but none of those efforts will lead to obvious advantages with enough appeal to switch large numbers of people to WP, particularly not those who are becoming ever more entrenched in the Google and Apple ecosystems.