But I feel that aggro doesn't need those cards, in fact they don't really need tech cards at all. Sure they're nice but as long as there's cheap creatures to play Aggro will flourish.
The loss of Mal'ganis and voidcaller will probably make demons simply unplayable again. I feel voidcaller was what made a demonologist deck work, mal'ganis is very nice but I played a demon deck for a long time without him.
Oil rogues without oil is not likely to accomplish much, but maybe some sort of oil/miracle mix might be viable. Replacing the oils with cold blood or something.
Of course any and every mech deck will vanish.
Though in the end I suppose it depends on what comes next, I sincerely hope that the introduction of formats comes with a new expansion so that it's not a case of just losing a lot of cards but replacing them with something new.