You can spend last year's Treasures of Halloween points at this year's Treasures of Halloween event.
No immediate plans for the Kotl City spawning platform in the near future. That area was intended to be a catch all for future content that may not fictionally fit as nicely as we'd like. While I think doing a full on Martian Dreams expansion may be a bit of a stretch, who's to say that a future Halloween won't find some twisted astronomer trying to upgrade the Moonglow telescope using lost Kotl Technology, and inadvertently drawing the ire of a distant technologically advanced martian civilization? Those creatures running rampant throughout Britannia may seem out of place, but down in the Kotl City they would be a welcome addition to the corrupted technology that powers it. Despite any claims to the contrary, there is still plenty in Eodon without the Kotl City. Gotta stay tuned to see what madness we can dream up next down there