I have many MKV videos to be editied but Vegas Pro 15 still not support MKV. I'm very disappointed for 5 years. There is no good editor than Vegas. Video conversation takes long time and fails. When will Vegas ever support MKV???
I have no doubt the MKV container will be supported in a future release.
However, it's become a bit of a "garbage container" format because of all the unlicensed codecs being used by illegal download sites.
So, even if container support comes soon, there are plenty of MKV files that will never open natively in Vegas, at least not without dicey third party decoders. Two such examples are Divx and x264vfw.