That would take billions of dollars and I highly doubt Mike has that much laying around. It would take someone like Microsoft to even dream of somehow buying the Blizzard portion of Activision Blizz and I also don't think it is that simple since they are so ingrained in eachother now.
Would I love to see Blizzard get away from Activision? Absolutely but it's just not realistic unless they went bankrupt or something and just started selling off assets of the company.