17mil PS2 owners have PS3s? 4 million newcomers?

[wholikeswood]

" The PS3 cross-ownership rate with PS2 is about 80 percent, so much of the PS3 installed base is a PS2 consumer or had been at some point "

http://www.gamedaily.com/articles/news/wii-to-lose-market-share-to-99-ps2-says-sony/?biz=1&page=1

80% of ~ 21 million PS3 owners = ~ 17 million PS2 owners.

So 17 million PS2 owners (out of a total of ~ 125 million) have upgraded to a PS3.

Does my calculation make sense? If so:

a) is that a respectable number of upgrades fought for by Sony?

b) is ~ 4 million newcomers a respectable number for Sony to have got onboard?