If you read around, then you would know there is NO jailbreak currently released for the iPad 2.
The ONLY known userland jailbreak is by Comex which was on 4.3 and was patched by Apple in 4.3.1, and Comex has NOT publically released it. And no one knows if he will be able to release it since it uses some coding by Apple and would be illegal to release it like that.
So the short answer to your question, since there is no jailbreak, no one knows if it is "safe" to upgrade yet. HOWEVER, it is usually NOT a good idea to do so, but the ONLY known jailbreak is for an earlier firmware anyway.