In a few hours, Apple  will reveal the next-gen 4.0  software that'll run at the core of its next iPhone, the current iPads, and maybe existing iPhones too. Here are some predictions as to what the announcement is likely to include.
What it is: This is the big one--the ability to run non-Apple apps in the background, so that the code is still in action but not visible to the user. This is partly available already, but only for Apple apps (mainly on the iPod). But until now full multitasking has been verboten, with Apple citing the battery-sapping it would cause. The last big iPhone OS update included the release of "push notifications" as a partial solution, but that's far from ideal. Apple critics have been clamoring for the iPhone (and iPad) to get multi-task powers for ages, and it's deemed  likely that Apple's worked something out. It may be thanks to clever code optimizations, and it may not be full multitasking (Apple might retain some control over what tasks can run in the background, for example, or how many can run concurrently).
What it means: You'll be able to surf the web, and chat on AIM at the same time on an iPhone without having to re-login to the chat each time you switch between apps. Lots of other parallel-running apps may make the iPhone experience much smoother. The iPad, which is already a much more capable machine, will be literally unchained by multitasking, and able to show its true powers as both a media consumption, and content production and sharing device.
What it is: Apple's mobile advertising system , a product of its recent purchase of Quattro Wireless. Essentially it'll provide developers with a simple way to include Apple-served adverts into their apps in a sleek way, which will provide another potential revenue stream. We've also heard recent rumors that Apple's hidden some webkit-style "rich experience" code into the iPad SDK...it's dubbed AdLib, so you may expect Apple's ads to be more than simple banners (a little like Yahoo! has promised.)
What it means: iAd could result in a slight fall in App Store prices, as developers find ways to monetize apps that perhaps they wouldn't have considered before. As a user you may expect to see more ads in apps across the board. Apple will gain revenues, which will feed into its iPhone and iPad development. It also raises the stakes in Apple's competition with Google, which being scrutinized over its $750 million acquisition of mobile advertising upstart AdMob.
What it is: A front-facing camera on the iPhone is long overdue, since it would enable both 3G videocalling (which hasn't really taken off, and maybe Apple will be the key to its success) and iChat or Skype videoconferencing. We might not see this revealed  today, as Apple would be indirectly revealing its future hardware (the horror!) but it may be revealed in the code.
What it means: Pretty much what you expect: A richer, more video-centric iPhone experience.
What it is: Apple-sanctioned hooks in the software development kit to enable an iPhone or iPad app to directly access a networked or Bluetooth-connected printer  (or to easily reach one via a networked Mac or PC).
What it means: Easy printing of photos, maps, directions, recipes...or whatever tickles your pickle, direct from the iPhone or iPad and available at the flick of a switch inside an app (rather than having to use special apps, or awkwardly exporting printed media through a PC or Mac).
Bluetooth keyboard, iWork for the iPhone
What it is: An expansion of the iPad's powers to access full-size Bluetooth keyboards . And a porting of the refreshed iWork for iPad apps to Apple's other, smaller, mobile computer.
What it means: A transformation of the iPhone into a much more productive device for people who really like to do ultra-light mobile computing (with tiny, fold-up keyboards).
iLife for iPad, iPhone
What it is: Just like the new mobile iWork, a refreshed version of iPhoto  and iMovie with tweaked user interfaces that are more aligned with touchscreen browsing.
What it means: Much more powerful video and photo management while mobile. Given that we expect the iPhone 2010 to have an improved camera (both for stills and video) and that Apple may even dream up an official way to hook the iPhone's cameras to the iPad, mobile iLife would be handy. If it syncs seamlessly with the iLife software found on any Mac, it'd be an even sweeter deal. With these, and possibly even an iWeb app, the iPad would become a truly powerful content creation device.
To keep up with this news as it develops, and in the run-up to iPhone 2010's release, follow me, Kit Eaton , on Twitter. That QR code on the left will take you to my Twitter feed too.