According to an article by iDownloadBlog, there will be no more untethered jailbreaks for iOS 4 in the future. This means there will be no untethered jailbreak for iOS 4.3.4 and 4.3.5.
The reason is that these userland exploits are being saved for the release of iOS 5. Userland exploits are vulnerabilities found in the operating system itself rather than the hardware. These can be fixed in days by Apple. Unfortunately, these are essential for an untethered jailbreak, without them an untethered jailbreak cannot be developed.
Bootrom exploits however, are vulnerabilities found in the hardware of the device. These can only be fixed by a hardware update.
Different jailbreak teams are trying to find new userland and bootrom exploits. The userland exploits will have to be saved until iOS 5 is released, whereas the bootrom exploits will be saved until the iPhone 5 is released to ensure a jailbreak when it arrives.
iOS 5 and iPhone 5 are both expected to be released in the fall timeframe, meaning that if you have upgraded to 4.3.4 or higher, you’ll have to wait till then to have an untethered jailbreak.
Meanwhile, you can still jailbreak with the existing tools. Use our step-by-step tutorials to jailbreak your device: