We have no idea when Amazon will sell the K4's in Europe but I am sure that it is coming.
I remember that there was a problem with selling the K3 internationally and the US when it was first launched. The US supply was strong enough to handle demand but the international K3 seemed to have more then one supply lull. It might be that Amazon is intitially concentrating on the US and will release the international versions after the Christmas rush.
Amazon's main competitor is BN which is only available in the US so they are probably most concerned about countering the Nook Color, Nook Color 2 (when it is announced), and the Nook Simple Touch. Since those devices are not available outside of the US, it would make some business sense for Amazon to be focused on the US release intitially.
This post is pure speculation as to why the K4 is not available for order in Europe. The K4 Lite is already available internationally so I think the rest of the line will be available at some point in time. I would also guess sooner rather then later.
I do not think the Kindle Fire will be sold outside the US for a little while.