there have been a few releases in ogg format for some time, now nobody uses it anymore in favor of wmv and mkv.
WMV is proprietary crap. If you want to release the file as a mkv, great, go for it. Any open format is better than a patented one. I really don't see how mkv is more popular though. Ogg seems well supported by the tools I use (kino, ffmpeg, totem, vlc). I hadn't heard about mkv until recently. Also, a quick google fight:
"ogg file": 237,000 search results
"mkv file": 37,000 search results
"ogg video": 68,500 search results
"mkv video" 44,100 search results
I reiterate, I really care about codecs. The leading free codecs (theora, vorbis, flac, speex) are developed by the same group (Xiph foundation) that develops ogg. So that's what I use.