Because it's fun - what would make the ideal conference/system?
(Orange font fuck yeah)
<= £300
Slightly chunkier controller with the rumoured move functionality built in (scrapping the wand altogether), implement a universal share feature, give it a touch-screen keyboard and keep the damn charge cable.
PS+ same price as it is currently but with added Gakai service thrown in.
The Last Guardian, Dark Souls 2, Uncharted 4, new Eidos racer and new Sucker Punch game released in launch window.
Keep the XMB but streamline it further.
Not too bothered about this, but make Home something worthwhile - give the avatars the pace/freedom of Cole in Infamous and flesh out those projects like Xi, remove load times and have background downloads for new in-world locations. Cram in more text adventures and weird indie stuff. Maybe integrate it into a chat room when Friends are waiting in an online lobby. I don't know, but make it interesting and not shit.
Offer a reasonable backwards compatibility work-around e.g. PS3 disc recognition and download option (one use only).
Make a pledge to back more developers that produce games like Journey, and take more risks.
Pedant's desire - Make the PSN tag more customisable and allow people to flesh it out with a profile
(roughly 2% of this will actually happen)