What follows is information we were provided at a meeting this week of FIRSTWA. It's not confirmed until FIRST says it's confirmed, but I can't imagine much about it will change.
The biggest item of note is that the Seattle Regional won't be held in Seattle at all, but in Tacoma, WA. If you're not familiar with the region, Tacoma is about 25 miles south of downtown Seattle and 15 miles south of Seattle-Tacoma International Airport. It's far enough from Seattle that teams traveling from outside the Puget Sound region will want to find accommodations in Tacoma proper.
The venue is
The Greater Tacoma Convention and Trade Center in the heart of the city's downtown waterfront. There is no seating at this venue, so I understand they'll be bringing in bleachers for the event.
Capacity is 40 teams. I expect that growth in the area will mean that there are about 15-20 teams, maybe a bit more, within 50 miles of the venue. The balance will likely come from Oregon and British Columbia, but teams from Oregon will probably register for the Oregon Regional first. We'd love to see some folks from out of region come to visit.