It's a good point, and I haven't quite thought that through. I believe during the Acts period some were given a word of knowledge from God, specific to their church or to their small environment, which didn't make it into the Canon, but was definitely revelation. I believe something similar might happen during the Tribulation with the 144 thousand witnesses sent from God. I don't think that's happening today, though, or will happen during the rest of the Church age.
I'll have to give this more thought, however.