Hello Nicole,
This Disney Parks Moms Panelist is an avid caffeinated Starbucks coffee drinker and was beyond thrilled when Starbucks opened its door on Main Street U.S.A., back in June 2013, and continues to have locations percolating up all around the Walt Disney World Resort. After seeing your question, which obviously was meant for me, I, too, was curious if any Starbucks mugs had yet to adorn the shops with the Walt Disney World/ Disneyland logo stamped on them.
With the help of a Cast Member, involved in Merchandising for Walt Disney World, I was informed, "at this point," none exist but to keep an eye on the
Disney Park Blog for any further updates. With a little bit of Faith, Trust, Pixie Dust and Coffee Beans maybe some will brew up soon.
If I can be of any further pixie dusted assistance feel free to ask and may your upcoming stay at Walt Disney World be filled with many magical, memorable and caffeinated moments.
Amy M*o*