Objective-C is not a brilliant language and it's finally being discarded by Apple and replaced with something better. This is hard to accept for the (surprisingly) many fans that it has, but Objective-C is almost legacy - jobs, docs, APIs will be Swift-first. Talking about performance and dynamic typing and message passing won't change that.

Apple looked at the competition and saw that Java 6(!!) was kicking Objective-C's ass - it was easier to program in, less error-prone, easier to understand and fast enough.