My wild guess is that it will be added rather soon than later to CIDER. The protocols are part of Clojure, and Emacs is great with browsing buffers, so it doesn't seem very hard to implement.
That said I'm not Emacs expert so it may be harder than I imagine.
Everything except HTML and charts will be easy - after all, if something can be represented as or drawn with plain text, Emacs is probably the best tool for working with it. HTML has some half-decent previewers available, but those are essentially text browsers in elisp. Unfortunately, painting arbitrary images gets unwieldy with Emacs. You can get away with ASCII column charts, but forget scatter plots or sparklines. But for viewing that, I wouldn't mind an external application to put on another screen.
That said I'm not Emacs expert so it may be harder than I imagine.