I have no particular insight into the iPhone OS development. I don’t have sources. I’m not an iPhone developer. But, since I found myself thinking about it earlier, I came up with a few things I’m hoping Apple announces as part of iPhone OS 4.0. I’m not claiming any particular ease, but these are generally things I think could be implemented elegantly and straightforward for the vast majority of users.

• Multitasking. If they stopped here and allowed me to background Pandora, I’d be happy. If I was drawing up the feature, I’d have people explicitly ask for certain apps to run in the background vs. everything automatically getting to run in the background. With limited memory on the iPhone, iPod Touch and iPad, users are going to have to specifically request a small subset of apps be able to run in the background. I can see this being limited to the iPhone 3GS and iPad since they have 256 mb of RAM.
• Fast user switching. Or, some other method of allowing an iPad to be used by multiple people in a family and keep settings straight.
• A more mature mechanism for notifications. As Fraser Speirs has requested, the ability to have a notification quiet period would be nice. There’s also room for having a way to review all notifications, particularly if you have several of them.
• New maps features including cycling directions, terrain tiles and, for the iPad, street view.
• Lock screen widgets. The iPad has the slideshow. I wonder if Apple might add the weather, the stocks widget or something similar.
• Lock screen emergency number dial. There’s a number to call if your phone is found or you’ve been involved in some manner of accident.
• Unified inbox for Mobile Mail.
• Email signature differentiated by account. I’d like to keep the same signature for each domain I send from the same as my desktop. The iPad (as near as I can tell from the Mail guided tour) doesn’t offer this, but it would be a big step forward to thinking of it as a primary tool if it did.
• Multiple Exchange-account support. Alternately, push support for Google apps like Mail and Calendar. Right now, the iPhone is limited to one Exchange account for email or calendars. If you have multiple GMail or Google calendar accounts, you only get push support for one (by way of the Exchange functionality).
• A better document management method. Maybe it’s MobileMe, maybe it’s a Time Machine-like hands-off sync mechanism. Maybe iWork gets more robust. But somehow, someway, there’s something better than what John Gruber describes in his iPad review.

What I’m not expecting to see

• Wallpaper on the iPhone. The app icons are too close together to really make out anything else.
• Turn-by-turn navigation. I don’t have a great reason, I just don’t think it’s going to be there.
• Video-conferencing support. I believe Apple’s thought this through and thinks the experience of holding a device in front of you for a video conference is going to suck.