Abstract methods in Swift?

As of today (April 7, 2016), the proposal to introduce abstract classes and methods to Swift (SE-0026) has been deferred.

Joe Groff posted the following in swift-evolution-announce on March 7, 2016:

The proposal has been deferred from Swift 3. Discussion centered around whether abstract classes fit in the direction of Swift as a "protocol-oriented" language. Beyond any religious dogmas, Swift intends to be a pragmatic language that lets users get work done. The fact of the matter today is that one of Swift's primary target platforms is the inheritance-heavy Cocoa framework, and that Swift 2's protocols fall short of abstract classes in several respects [...].

We'd like to revisit this feature once the core goals of Swift 3 have been addressed, so we can more accurately consider its value in the context of a more complete generics implementation, and so we can address the finer points of its design.

I encourage you to read the full email, but I think the conclusion is the same as what you came up with in your question: we're currently stuck with the Objective-C way of doing things (raising exceptions).