Normally I wouldn't write up a whole post just for one figure, but this is a special case.
Doom Stone is the final swappable SWAP Force character that we've all been waiting for. According to the Toys R Us printout pictured below, Doom Stone will be available on May 13th.
As I said, this is specifically for Toys R Us. I still do not have confirmation of when he will be appearing at other retailers, but I'm sure it will be soon. (At least I hope it will be since I still don't have a Toys R Us nearby.)
Kickoff Countdown Release Date
This page from an upcoming Toys R Us ad has leaked. The ad is for the week of May 18th.
The ad states that you can get Kickoff Countdown first at Toys R Us. This is not surprising as Toys R Us has been getting a lot of early release dates for Skylanders.
So there you have it.
Doom Stone: May 13, 2014
Kickoff Countdown: May 18, 2014
Jade Fire Kraken is still a big mystery. You'll probably see another post like this one once we know more.