They've always depended on the international crowd pretty heavily. One, because their attractions don't rely on U.S.-oriented IPs or "American humor" (or in most cases even require you to speak English), and two, because more international guests have more days of vacation to fill. I agree a drop in Brazilian or UK guests absolutely kills SW.
That said, I think a large chunk, possibly a majority, of the remaining 2/3 of guests are locals.
For their CEO saying they don't want to be the "discount" park in town, a ton of billboards around town advertising $69 tickets and e-mails saying as an AP I can get 4 and 5 year-old in for free all year. Mako looks amazing, but I still don't see it being enough.