In agreement with others, my understanding is that there is that there is a resident population in the Lake Wenatchee corridor, with transients to at least Cle Elum. I would guess that there are some moose in the Methow and lower portions of the Pasayten who are at the least semi-resident. Many areas around Ross Lake would make attractive moose grounds for transients from the Methow, Wenatchee-Chiwawa system or from BC.
Anthropological evidence primarily from Indian middens shows that Native Americans feasted on moose in these areas at least to the late 1800's. Evidence of moose in the Cascades became sparser, but not non-existent for about the last fifty years. There definitely seems to be an increasing population of transients and marginal residents on the very south western (the North Cascades) extent of their range.
Since NE Washington has had a strong population, and even then less that 150 moose are allowed to be taken, I would guess that the Cascades maintaining a moose population large enough to allow hunting is unlikely. But given the changing dynamics of rainfall and snowfall, many things are possible in the long term.