POINTS TO PONDER: What's after WYY?

As per title, what comes after WYY since now already "WSS"? Anyone know?

Could It ended up like Sabah "WAA1234A", with the last digit move 1st until "WAA9999Y" then "WAB1234A".

OR Could it ended up like most of us predicted "WAAA1234"? Ladies and gentlemen, What's your opinion?