Honestly, he might as well just reveal the roster in the two weeks prior to launch.
It's not like we won't know THE DAY of the 24th anyway. We had pictures of the Japanese roster from SSBM the same day so I expect this to be the case for Brawl, unless Sakurai put in some fiendish code which makes it so you can only unlock one character per day and uses an online clock to synchronize so you can't just set your Wii's internal clock to fool it.
Besides, unless all of the secret characters are heinously obscure, they could be used to hype the sales of the game up even further. I expect him to reveal any remaining 3rd party characters before launch, since they'll DEFINITELY add to the hype.
I'd rather know so I can get the disappointment over with ASAP, and if I'm not disappointed, good, but I'm still concerned enough to want to know now instead of later.
Oh, and I was right on the money: two weeks of hype-inducing updates before launch.
I'm actually glad he's shutting the blog down for now. I'd rather wait until the 7th and get some sleep than stay up every night only to be disappointed by a crap update.