This can be a bit of an @rseache to be absolutely honest bud, there are an increasing number of TVs which (claim to) have MKV support; but exactly what that support runs to is rarely (if ever) specified.
The problem is that MKV is essentially a container, a wrapper. Inside it are (normally) are at least two items - a video stream and an audio stream. As I'm sure you're aware, very often there are lots of items in the wrapper (in terms of multiple audio streams, subtitles etc.). The problem though, is that where as normally, anything on a shelf in the same wrapper will have the same contents; it doesn't work like that with digital AV files. The contents of two things inside an MKV wrapper can differ wildly.
The range of different compression/encoding formats used for video and audio inside an MKV files is what makes finding the right telly to do it natively a bit of a nightmare.
The issue is that not all tellies can cope with all the compression/encoding variance, in fact, very few can. There can be issues, even with commonly used HD video compression (the 264 variants), at higher bitrates; audio can be a stumbling block too, since not all sets will be able to natively downmix for example, a DTS encoded audio track.
To be honest, the best thing I'd suggest is choose a decent set given all the standard factors you might consider: Size, Panel type, I/O connectivity, quality of upscaler (if you're ever likely to watch any SD video on it (*nods furiously*)), etc.; and then buy a separate, external USB-HDMI AV playout box (Popcorn and the like); they've got massive advantages in compatibility and performance, and of course development of fixes, improvements and new features doesn't just stop at the release date. I can count the number of television manufacturers who have any sort of MKV container support over USB natively, who really put effort into continuing development of software on 0 fingers.
Sorry, that's the second AV related question this week I've wafflled/almost ranted-on, my defence is that matters of AV tech are my 9-5 bread and butter.
All the best,
Rob.
