Anders,
Catalyst 3850 will be available with 12- 24-port 40G QSFP in the coming months. It has no dedicated stack ports, but can stack through the QSFP's.
Catalyst 6807-XL and Sup-6T are a different story... Although initially advertised as "optimized for 10 / 40 / 100 Gbps", the latest 6807-XL data sheet has been scrubbed to read "optimized for high-density 10 Gigabit Ethernet and capable of supporting 40 Gigabit Ethernet." The Sup6T architecture doc still refers to "Next-Generation Line cards" and you can even find pictures of them suggesting a release date of Q3 or Q4 2016. They hopefully will be released, but you shouldn't hold your breath...
Within Cisco, the Nexus 7K products are now under the business unit responsible for Catalyst switching products, and partners have been told to lead with Nexus 7700 instead of Catalyst 6800. E.g., a Nexus 7706 has twice the port density as a Cat 6807-XL, and the ports aren't oversubscribed.
-Craig