Hi,
SpringSurf and the various core libraries it entails are still the web and REST framework that underpins the core of Alfresco Share, Alfresco WCMQS and other Alfresco apps. It is not going away regardless of the state of the Spring extensions. The discussion currently is around what is the future direction for the Spring Extension i.e. the uptake and interest of WebScripts and SpringSurf as separate Spring hosted libraries is low and there is discussion around the value of it being a separate externally hosted library. As far as actually using it internally - WebScripts is the REST API framework of choice for Alfresco, Surf and YUI are component page composition framework and JavaScript framework of choice for Alfresco applications. The customisation and extension features of Share 4.0 are all built on WebScripts and Surf.
Cheers,
Kev