What I wanna know is if it locks the other way around, on BETA the last time I checked if you did mythic and then mythic+ in the same dungeon you got lootlocked in mythic+ and got no loot from the reward. This still the case?
I did some Mythic+ dungeons last night and (as far as I can tell at this point) I am not locked out of doing Mythic dungeons for gear. Since Mythic+ doesn't have gear on the regular bosses it's not likely to loot lock you per boss.