I don't think they will tbh, the other games never really did that on PS3 and even Dissidia NT hasn't done that and that's a KT game in the same boat as DOA6 except for good xD no servers also means they'd have to likely stop selling dlc like Tekken revolution and SC lost swords
DOA5/6 can probably run forever on PC online though since there is a life span for older gen consoles, not much to say on that unfortunately, especially since the console versions have lobbies.