Consider this to be your 6-month warning. Like the Challenge Mode armor from Mists of Pandaria, the Challenge Mode weapons from Warlords of Draenor will probably be going away forever in the 7.0 patch. I remember the mad rush for people to complete the MoP CMs in the final days leading up to 6.0. I knew people with the gold to spend on carries who couldn’t get it done in time because of the sheer demand those carry groups were under in the final days. So if you want these? Don’t procrastinate!
What’s more, it looks like Challenge Mode transmogs will be going account wide for the same class. So if you unlock this stuff on a Hunter, theoretically you should be able to use it on any Hunter on your account. For someone like me who only plays Hunters this is pretty cool news. There’s no word yet if the weapons you unlock will be usable on other classes though. For example, Hunters can buy almost all of the weapons (except for a few), but I’m not sure that means you could use the 2H sword on a Warrior alt (don’t count on it).