Each time Apple releases a new upgrade soon after a major jailbreak is released, it is fair to expect that the jailbreak exploit will be removed. As you know, the Cupertino Company is trying hard to plug the security holes that make jailbreak possible. Along with the release of iOS 7.1 Beta 3, a minor software update that is not yet ready for a public release, Apple did not remove the security gaps that facilitate the Evasi0n 7 jailbreak.
As confirmed by the iH8sn0w, the beta version does not patch the jailbreak, but this does not mean that the final version will do the same. However, this is not something uncommon. So far, there were plenty of betas released with minor end-user updates that passed after a jailbreak without plugging it.
While Apple is fighting against jailbreaking, jailbreak developers have gathered together in order to develop a proper jailbreak tool that will perform jailbreak on iOS 6. Since each iOS becomes even more jailbreak-proof than the previous one, developers have managed to find a way in order to employ the security exploits to develop a proper jailbreak tool.
The same happened in the case of the Evasi0n7 for iOS 7 jailbreak. While some have doubted whether the team will be able to find a way through the Fruit Company’s security branches, the jailbreak team released Evasi0n7 after several months of iOS 7 experience.
However, despite this great news, it is better for you not to upgrade to the latest Apple’s beta firmware. The best is for you to stick to iOS 7.0.x in order to avoid further complications; this is recommended only if you value the ability to have a jailbroken device.
As recent news confirmed, it appears that the Russian developer smolk has released a patched version of Evasi0n7, which performs a successful jailbreak on iOS 7.1 Beta 3 on all supported devices. However, it is advised to wait until further news regarding this topic are released and do not try jailbreaking your iOS 7.1 device via unofficial means.