Going forward SharePoint Feature Framework will be replaced by SharePoint add-in model. SharePoint add-in model is just a new name to the SharePoint App model. Only branding terminology has changed. But we as developers need to follow the right terminology.
So unless you are extending SharePoint or customizing SharePoint Server product which required full trust solutions, as shown in below snapshot, add-in model is the way forward for implementing customer specific customizations . These add-ins does not necessarily means that SharePoint is to be deployed on cloud or that they are only applicable to Office 365; add-ins are applicable for on-premise installations as well.
The key recommendations coming from the Microsoft SharePoint team is
- Move gradually to add-in model.
- Align with service and product roadmap.
- Concentrate on end user experience and business requirements.
- Avoid sandbox solutions.