Apple has many, many more deprecated classes and object than that. Perhaps those are just the ones you are using.
I can guarantee you that Apple is not going to tell you any dates - not for UIWebView and not for anything else either.
Obviously you will have to deal with the UIWebView deprecation. Apple wouldn't be issuing that warning if they didn't intend to do something about it. All too often, developers just ignore those warnings and keep on coding. Don't do that.
But on the other hand, if you aren't getting a warning like that, you may be able to just ignore it. If there is a newer, supported API that works, then, by all means, use the replacement. But, in many cases, Apple just deprecates things without providing a newer and/or functional API. What are you supposed to do then? Discontinue your app? File a bug report? LOL