AHA!
http://wii.ign.com/articles/707/707504p1.html
E3 2006: Super Smash Bros. Brawl: Wii's big brawler is full of surprises.
First details and screenshots inside!
May 10, 2006 (See that date?)
"Even better, the game will be fully online playable in addition to featuring a robust multiplayer mode. "My plan is to include Wi-Fi connection compatibility and online functionality. One of the primary reasons Super Smash Bros. Brawl was created was that Nintendo, when taking Wii online, wanted to have Smash Bros. to do that," added Sakurai."
Right there, months before the Wii even launched, online was confirmed. The details were not there, but Nintendo was evidently working on that.
Now this isn't the interview I mentioned about how Sakurai didn't feel that online isn't the best experience for this game*, but that wasn't telling us online was out. Nintendo never did that.
However, this was given at the same time Solid Snake was announced as a character, so people were evidently too excited by that news to notice the announcement of online.
So this recent news was not an announcement of online, but of the details.
*Now don't ask me for that link. I can't remember the key words to google it, and I can't even find the link in the message board where I found it, since that board has flushed its archives.