Swift seems to be bringing in developers with backgrounds in other languages who are not familiar with Objective-C. I'm sure documentation in Swift syntax will come soon. But if you do plan on doing serious development for OS X/iOS you still should probably take the time to learn Objective-C. It's still too early to tell if Swift will end up "replacing" Objective-C or if it will be another tool in the toolbox that will live alongside Objective-C. Either way, it will probably be years before Objective-C becomes obsolete (if ever).
It definitely is worth learning, I think. But then again I really love the language. I love the verbose method names that read like sentences. It encourages programmers to write readable code. I'm sure I'll end up loving Swift too eventually. Not sure if I'll love it as much as Obj-C though. Time will tell.
Probably for several years, serious Mac and iOS programmers will probably need to know both languages.