It's now possible to jailbreak the iPad 4.3 Beta with a PwnageTool bundle released by iPhone hacker Johnny Franks. The bundle works with the current version of PwnageTool for creating a custom firmware.
The downside is that this is a tethered jailbreak, meaning you will have to plug your device into the computer anytime it's rebooted.
Remember that iOS 4.3 Beta is only available to developers, and you will need a developer license ($99) to download it.
All that said, we probably wouldn't try it out, so only do so at your own risk.
Here's the link to the PwnageTool Bundle.
Still, you can learn how to jailbreak with the following tutorial: here.