In their day (1950's and 60's) those were all solid companies, but companies that existed in the modern world and sold their goods and services to the consumers visiting Disneyland. Carnation milk sponsored the Burns & Allen TV show that was very popular to 1957 visitors to Disneyland, and Hallmark and Bekins and Timex and Kodak were all modern brands living in the modern age beyond the berm, while selling their modern wares inside the berm. Upjohn Pharmacy passing out free vitamin pills on Main Street was the CVS or Walgreens of its day, and you can imagine the horror if CVS put in an old-fashioned pharmacy today.
The Starbucks will be gorgeously themed and lovingly decorated. And it fits perfectly into not just the building, but into Walt's original vision of Main Street and Disneyland as being a showcase for American Free Enterprise and the best of American commerce and industry.
And it will be wildly popular with paying visitors, too.
I would also say that the equation of Starbucks with Walmart sponsoring the Emporium is wildly inequitable. The more equitable analogy would be if Starbucks was on one corner, while Nordstrom sponsored the Emporium on the other corner.