I wonder how the Pi 4 will behave with enclosures such as these that are basically one large heat sink for all chips.Would make it easy to carry around also. I refuse to rely on active cooling. A Pi has to be completely silent to begin with, and I travel quite a lot so the less parts and wires that can break the better.
I'd expect that to work well assuming it is a large piece of aluminium with good thermal connection to SoC.
Flirc cases have historically worked very well using the same principles.
I'm also expecting the new Pi4 version of Flirc case to work well when I get to try one.