Based on the 7000 series user manual on the Samsung support site, yes to MKV. Download manual for full details.
Dvix 3.11/4.x/5.1/6.0 - 720x576
XviD - 1920x1080
H.264 BP/MP/HP - 1920x1080
MPEG4 SP/ASP - 1920x1080
Motion JPEG - 800x600
What codec and formats does the B6000 and B7000 LED LCD's support? Do they both support MKV?