Not really. Price point would never be competitive. We might be forced to pay to play online games. They would have only control over it.
If you think about it really though if services like OnLive, Playcast, OTOY, GaiKai are popular enough they could be launched on the consoles and portables as well and then all would be playing through one network anyway.
Not really since I think the PC is for people who don't like owning so many systems.
It would be neat to make a cheaper console without the DVD/Blu-ray drive, and you can just plug in and use an external USB Blu-ray/DVD drive to play your games. It will make replacing a dead DVD/Blu-ray drive easier without the need to open the console.
Yeah it wouldnt work, sony, microsoft, and nintendo would fight over everything. (Online, price, pay to play, games, design, everything) All companyies are unique so keep having 3 unique systems to choose from, the only downside is you get the stupid fanboys trying to make it like their system is supreme, i hate those people!