Log into your account and click on Register for Special Offers. What's in there is all there seems to be right now. I have just a few miles offers, including triple Southwest Airlines (600 + 1200 = 1800 per stay) through mid June.
Their current non-miles promotion ends on Sunday May 8. Perhaps they're waiting until it ends to announce the next non-miles promotion? Or perhaps they have a period of no (non-miles) promotions between the end of this one and the summer one?
The current one is
www.bestwestern.com/spring; I've been trying
www.bestwestern.com/summer daily, but so far it just says the promo "is no longer available" (presumably because it's referring to last year's summer promo; they tend to re-use the same web links every year).