ZigBee is moving in the same direction with DotDot, but I found Thread’s agnosticism (in regards to application layer traffic) to be refreshing. Bluetooth’s mesh is very, very immature, at least what they have released so far.
The fact that ZigBee (application layer) requires data to go through a gateway via a standard before hitting some server on the internet is probably a very good thing for pushing interoperability. What you see with IP bulbs is that each bulb hits its own servers on the internet -- when that business disappears in a few years, the customer is probably SOL.
ZigBee app layer on Thread (DotDot) will probably be pushed more. Just a question of whether the advantages of Thread over Zigbee (3) will have enough benefits to push ecosystems like home automation to switch over to this stack.
ZCL is not exactly RESTful, so running it with URIs over CoAP is still a little weird. It’s main advantage is being able to run all the same application code on your devices, regardless of networking (WiFi, Thread, BT, or ZigBee).
I don’t know how that will turn out in practice, but ZCL has wide adoption, and Thread required you to develop your own application layer. So, it has great potential, I guess.