As in raw assets and materials?
I really miss all of the good stuff that was in UDK. 
There’s more content in the pipeline that will be available in Marketplace over the coming months!
Just export the meshes from UDK and rebuild the materials 
^ I’ve been doing a little of the above, so long as you aren’t redistributing that content it should be fine. But yeah, I think that’s what the marketplace is for chap 
Don’t forget that all the content is interchangeable in terms of scale etc… so you could in theory copy all the assets you have to far into one project if you want to experiment with things. I imagine the Elemental Demo will be quite a huge download.
The materials are slightly tougher to port from UE3 (or ANY game really) than the meshes oddly enough, just because of the new PBR system.