There are 2 seperate questions here:
Is there ever any likelihood of this being a supported device
I assume you have already done a proper Forum Search for your model number in case other people have already answered your question ?
If so and that didn't help then check out this thread: https://community.sling.com/thread/3300?tstart=0
Come back if it that doesn't help either
to play on ordinary or smart TVs?
At the moment the only way to show a Sling stream on an ordinary or smart TV is via another box (Slingcatcher, Boxee).
There was a forum entry on 23-Feb-2012 09:42 and the reply was that the SMP-N200 was an unsupported device.
I thoiught it was fair question since I have one as far as I can see it is similar to WDTV or Boxee (and I presume Slingcatcher, but it seems in some forum entries that people are saying slingcatcher is no longer available).
Sorry, you're right, it was a fair question, it is just that I had no idea what a Sony SMP-N200 was. I had assumed it was a normal STB/PVR/Satellite/DVD device that wasn't supported when you tried to install a remote. So in that context your question made no sense.
Now I have googled 'Sony SMP-N200' I understand what you are saying. And I guess I would say no I would have thought the ROKU box was ahead in the queue, and there is no sign of a Slingplayer app for that. And you are right, Sling have discontinued the Slingcatcher, although you can still get them on E-Bay.