Would that information some how become worthless?
Let's take an even simpler example (from Broodwars): For a long time every Protoss and their mother would run 5 gate. What do you do against 3 base Muta? 5 gate. What do you do against +1 bio? 5 gate. What response to Mech play? 5 gate. PvP? 5 GATE! There was no Protoss strategy but the 5 gate, and all others were pretenders to the throne.
Now obviously the standard play is no longer 5 gate, a quick look at the quarter finals of the OSL will show that the 5 gate is long dead, so what use does an answer about countering 5 gate have?
When 5 gate eventually fell (and it did) it was to new kind of tactics (eg. 2 base Muta) and it was the inflexibility of 5 gate to deal with these earlier strategies. When it ran into this situation what do you think Protoss did? 4 gate, 3 gate, 3 gate robo, etc. Because those strategies has larger flexibility to deal with earlier pushes.
Today these, counter 5 gate, strategies have also fallen, so does that then mean the 5 gate will come back in to play? As a new player I might realize, "Oh my god, if I can get 5 gates and just macro, I can curb stomp anybody!" To this new player, knowing what the weakness of 5 gate is, is still useful. What's more, what happens when some player does go 5 gate against you? Even though its no longer a common strategy there really is nothing to stop someone from doing this? The information about what makes a 5 gate inflexible and how to deal with it is still useful.
Now you might say, "sure that works for the meta game, but what about when MK gets his storm bolt nerfed?" Well I'm glad you asked faceless straw man. Those strategies used to counter Storm Bolt sniping, are still useful against the MK. Even though he no longer is able to easily snipe towers, he hasn't disappeared from the game. Information about him and his abilities persists. Sure certain details of the answer will go out of date, but if its a good answer, the concepts that it teaches should still be relevant.
On the other hand, if you're worried about people trolling out of date answers, we can always just lock them and keep them around.