Of note to speculative poets is "The Sixth Sense" theme at the Tanka Cafe. In addition to Michael McClintock's introduction to the theme premise and a poem by Peggy Heinrich, there are nine pages of tanka alluding to premonition and extrasensory perception. I wouldn't necessarily classify all of these poems as speculative, but many of them are and should be considered Rhysling eligible. I am going to see if I can get permission to post a couple on my blog.
Speaking of speculative tanka, a tip from M. Kei led me to discover that Doorway to the Sky by Noriko Tanaka contains a number of ghostly and magical tanka. It was translated in 2008 into English by Amelia Fielden. I'm not sure where to order a copy, but will post the information when I receive it.