Apple is planning to Swift 4.0 expected release late next year while the Swift 3.0 is still fresh. From memory ownership model to resilience to strings with an emphasis on ABI stability for standard library and source stability for code is what will be included in the update according to a report. Along with this, the company is splitting the Swift 4 release into two stages. ABI stability and Source stability considering features that do not essentially change the ABI of prevailing features in the language or suggest an ABI-breaking alteration to the standard library will be included in the first release. Adjustments to provision code bases leveling different language versions are included in the High-priority features backing stage 1 goals, so Swift can supply on source compatibility goals while progress endures.
For APIs to evolve while maintaining the ABI the company is looking for resilience in stage 1. This will eradicate the flimsy base class problem that arises in some object-oriented languages by unfolding type of API changes, which can be made without breach the ABI. Generic improvements needed for the standard library has also looked upon by the company. The implementation of stage 1 features cresting and a few other small and large improvements will be included in the Swift 4.0 stage two development.