Especially interesting because MS is trying to also stay in the phone market, and the two device types have significant market linkage.
Based on MS' recent (like, 10 yrs) history, you'd have to give MS less than even odds that it will succeed. However, The big difference between then and now is that we now know what works in both tablets and phones; before, everybody was thrashing around. There is unlikely to be another disruptive design element soon; we're talking for now about linear improvements in functionality and pricing.
It's almost inevitible that Apple's market share dominance will eventually decline. It's just not clear who will benefit when it does.