Last year around this time, Starbucks was filing paperwork to acquire two buildings at 83 S. King St. and 505 1st Ave. S in Pioneer Square. It is confirmed that they are indeed extending their headquarters but it will be quite the process. 
Built in 1904 and renovated in 2000, 83 S. King is currently occupied by Starbucks employees in the Store Development Design and Pacific Northwest Region Store Development Team divisions. Other lease agreements within the building have been honored and Starbucks will gradually take up the space as it comes available. 505 1st Ave S. has been granted a master use permit for a 7 story, 203,000 sq. ft office building. A parking lot, parking garage and the one story, Duncan Building sits on the site and plans for demolition have not been revealed, let alone a timeline.
This is very exciting news for the neighborhood and a perfect fit for those condo projects just being developed/proposed in the Downtown/Pioneer Square areas. An update should be publicly released in the next month or two, so stay tuned!