I think that the analysts are simply going by patterns now, PS3 increased 2008->2009 so it should increase 2009->2010, Wii and 360 decreased, so they should decrease again.
I can see the PS3 increase, maybe by even more than 10%, but it completely depends on the games that are announced during E3.
Wii? Dunno, can increase, can decrease (not by 20% though, 10% at "most"), depends on how long the NSMBW momentum goes, the vitality sensor games and whatever is announced in E3 (SMG2, MH3 and M:OM won't make a difference).
360? I think we will see a decrease, but it completley depends on Natal's success.
Bet with Dr.A.Peter.Nintendo that Super Mario Galaxy 2 won't sell 15 million copies up to six months after it's release, the winner will get Avatar control for a week and signature control for a month.
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