Release cheap and first. I know that doesn't make much sense since they released last this gen but since they'll likely be the only manufactuer to keep supporting there past system an early release of the PS4 shouldn't harm the PS3s life-time too much.
As for features and whatnot I want PS3 bc-comp obviously, and PS2 and PSX. I'd also like to be able to buy and play PSP1-2 games on my PS4. This way even those not interested in portable gaming can get into these and it should mean more sales for Sony too.
I want a better, more welcoming UI. Whilst the 360s feels cluttered Sonys feels a little... cold. This can be done easily by giving us better themes allowing users to personalize there own XMB.
Graphics wise I want everything at 1080p, no higher. No need. The graphical standard should be Killzone 2 or higher for every game.