While Xbone sales is tanking (77K in May NPD), WiiU is enjoying a renaissance (67K in May NPD) due to MK8. Then Nintendo came out swinging at E3 (although I think Sony still won E3 with Bloodborne) which I think will generate more buzz for WiiU post-E3. Meantime all exclusive rumours for Xbone didn't materialize at E3. Xbone came out limp.
So what are the chances of WiiU outselling Xbone in June? as a playstation gamer, I have to say WiiU starting to look mightily attractive