They can and currently do. Hell, the TYM Discord and the TYM forums themselves exist and don't overrule one another. At the end of a day, Discord is a gaming chat app first and foremost. Can it serve as an online resource database? With a ton of work, yes. Does it make forums obselete? Not in the slightest.Is it possible for Discord and Forums to co-exist? I'm not sure it has to be an "either or " question.
The way I have the TYM Discord set up, it doesn't at all attempt to invalidate the forums. It just serves as a way for TYM members to gather for much quicker and fluid conversation, like a chat is meant to do, as well as providing an easy voice chat option for the community.