Any tablet able to play M2TS or MKV files?

I would not know the answer to your question too but I can offer to you suggestions on how to go about finding the right tablet/s. That would be --- what are the requirements in order to play what you want to play? Only then can you determine which is the best.

What operating system are they running? Usually the ability to play types of media files is a software issue as opposed to hardware. There are a variety of media players available that can play both those file types, VLC for example, as long as there are not extenuating circumstances (ie trying to play 1080p movies on low end hardware)

Any tablet can play mkv video. But it depends by CPU (720p/1080p) and installed video player.

My Transformer TF101 plays 720P just fine, sometimes chokes on 1080P. Since tablets are wireless, you may find that you have problems streaming 1080P, it can be a problem no matter what device you use. If you are going to store the file on the tablet, you won't fit too much 1080 on it at one time due to file size.

So,, I'd plan on primarily sticking with 720P or less content.

MX video player is a free app that plays most file types. I've played some MKVs with no problems.

I have an iPad and have installed Plex. I run the Plex media server on a mac mini which is tied to my drobo for storage. I can stream/play m2ts and mkv and nearly any other video format.

Give that a look.