If this was a firmware update, then no you could not revert back to older firmware (unless the Team does it for you), but this is an IPTV Buzz 4 app update and does not include a firmware update.
So theoretically you could revert back to an older Buzz4 app.
You would have to delete the newly installed Buzz 4 app thru you Settings functions and then go to Market and install an older version of the app.
But upon looking in the Apitode Market, I do not see any version of the Buzz IPTV app available in there.
So, unless I missed something then no, the user can not revert back to an older Buzz IPTV version.
I had a glitch with another box (not a Buzz box) that also recently sent out an IPTV update.
So what I did was delete that app and re-installed it from the market and all went well with that.