IMO (very likely with regard to the 360) it's likely to happen looking at the PS3's games line-up, feature set, specs, future outlook (cheaper PS3 slimline combined with PS2 to be discontinued at some point, HDTV uprise, etc)
The 360 should be no problem (90% of current installbase are coming from XBox background according to analysts, the pool of upgrading XBox users is rather limited, initially upgrading happened faster due to the demise of XBox software support), with regard to the the Wii it would be interesting to see how much Nintendo will be able to attract new kinds of gamers and how many will own more consoles for the future besides just a Wii (as for example demanding games make more sense to play on more powerful hardware).







