Only a few days after the launch of the iPad, Apple has announced the next event that will give its loyal followers something to worship. The company will be offering a sneak peek at version 4.0 of the iPhone operating system this Thursday, April 8, at 10 a.m. Pacific time.

Apple has done this in the past for previous versions of the iPhone OS around this time of the year, which should put our expectations in order. We’re likely not going to see any new hardware, for one. But this year things are a bit more exciting since Apple has the iPad in play, which also runs the iPhone OS.

Currently, the iPad runs iPhone OS 3.2, while the iPhone and iPod Touch are running OS 3.1.3. Apple could conceivably keep the iPad on a separate version of the OS from the iPhone, but I think it’s far more likely that it would consolidate all of the devices onto a single version of the OS. Despite the size difference, the iPhone and iPad don’t differ greatly in terms of hardware, and that hardware gap will be further minimized if the next-generation iPhone also runs on the Apple A4 chip (and it most likely will).

In terms of new features, we can expect a demonstration of the rumored multitasking implementation — the ability to run more than one application at once — that we reported on several weeks ago. While multitasking on the iPhone has been rumored for a while, this time around it seems far more certain. The existence of the iPad, in particular, demonstrates the pressing need for multitasking in the operating system. Otherwise, the limitations of the iPhone’s current single-tasking focus will soon become apparent to iPad owners as their honeymoon period ends, and the reality of the device’s capabilities become more clear.

Multitasking was also one of many aspects of the next-gen iPhone that Daring Fireball’s John Gruber hinted at in a recent post. Gruber has historically predicted upcoming Apple hardware accurately, and his certainty in the specifications seems telling. He also mentioned the inclusion of the A4 chip, as well as a front-facing camera for video chatting. I don’t suspect that Apple will demonstrate video chat in OS 4.0 at this event, since such a feature would imply a front-facing camera on the new iPhone, but it’s definitely a feature that would make sense to include in the next version of the iPhone.