Apple has sent invitations to the press for a special invitation-only event that will “peek into the future of iPhone OS.” The event will be held on Thursday, April 8.

As evidenced by the graphic on the invite, it’s almost certainly to be the unveiling of iPhone OS 4. The sneak peak will be held at the Apple Town Hall at the company’s Cupertino headquarters.

So what will iPhone OS 4 offer? Only Steve Jobs and Friends know, but it’s speculated that it will include more multitasking. iPhone OS 3.x (the current version) only allows a few core apps, such as iPod and Mail, to run in the background while another app is active.