That the SDF is in truth an army is something of an open secret in Japan. Pretty much everyone is well aware if it, and ordinary Japanese even sometimes use the word "army" instead of "SDF".

Public opinion still seems to be mostly against changing Article 9, which may be one reason why Abe has found it so hard to do despite putting all his political force behind doing so for the past several years. But like you say, it may not make any difference. Just as US presidents go around the US constitution and no longer ask Congress to declare war but go ahead and send in troops themselves, so too will the Japanese gov just ignore Article 9.

Will that make a difference? I suppose it depends on what the US demands Japan do or what rightwingers manage to gain power here in Japan.