We know its not this week because Kirby 64 is being released today. But here is what I'm thinking. Nintendo wants BIG money and they know that releasing SSB64 on VC will bring them tons of money. If Brawl is released before they release it on VC, many people will probably ignore SSB64 and play Brawl instead therefore lowering the amount of money brought in to Nintendo. Another thing that supports my theory is when MP3 came out, they had a Metroid Prime month and they released all MP 1 and SMP.
The only things that make it unlikely is that an N64 is coming out today. Its a great plan but Nintendo just needs to use it.