Oracle Application Framework (OAF) and Application Development Framework (ADF)
As of R12, OAF can only be used for Oracle Applications development/extensions.
Oracle ADF is an end-to-end J2EE framework. ADF is currently not used for Oracle Apps. Development / extensions. It is expected to be the case in Fusion and is a part of the Oracle Fusion Middleware。
OAF和ADF是Oracle的两个不同的产品。
ADF是在OracleAS产品线中的一个通用的应用开发框架，而OAF是OracleEBS中的技术组件，是EBS中所有网页功能采用的应用框架。
通常ADF会采用最近的技术，如果你做J2EE的开发的话，在应用采用ADF。如果你需要在OracleEBS上扩展和开发新的功能，则需要采用OAF。
ADF和OAF在很多技术上是相似的，比如OAF中采用BC4J的业务层组件，而在ADF中BC4J（ADFBC）仅仅是其中的一个选项。
当然了，如果你要学习ADF的话，OTN网站是一个很好的资源站点。如果学习OAF的话，资料相应会少一些，OAF自带的开发工具中会带一个Guide，也是比较详细的，我还没有发现其他资源站点。
至于ADF是否会取代OAF的问题，我想这本身不是一个问题。从技术的层面上来讲他们两个应该是一种技术，只不过适用的对象不同而已。
OAF provides you with automatic, seamless integration with the EBS applications in terms of EBS menus, security, look and feel, flexfields, personalization, attachments,
and so on. These integrated EBS features aren't part of ADF.
OAF Technology Stack for E-Business Suite R12：
OAF is a model-view-controller technology stack that is fully oriented towards EBusiness Suite application development. The OAF stack is comprised of underlying technologies like UIX and BC4J, that respectively form the core of the view and model layers（UIX是vier层的核心；BC4J是model层的核心）.It
includes Application Object Library (AOL) that provides common E-Business Suite artifacts such as menus, functions, messages, profiles, flexfields and attachments, and common services like function and data security.
MDS is used for metadata management. And finally, the OAF design time is integrated with Oracle JDeveloper 10g to provide a comprehensive integrated
development platform.
ADF 10g Technology Stack：
ADF is a comprehensive, model-view-controller technology stack that is oriented towards general-purpose application development. The ADF stack allows users to
select among several choices of UI and business services technologies. The ADF stack is primarily comprised of ADF Faces (which is based on industry standard
JSF technology), ADFm (m for model - the data control layer that implements JSR-227) and ADFbc (bc for business components – formerly BC4J). Early
releases of ADF contained UIX. Oracle then developed the ADF Faces set of components, based on UIX functionality, but conforming to the JSF standard. The
ADF Faces components now replace UIX as the preferred（优先选择的） view technology for ADF applications. ADF design time is also integrated with JDeveloper 10g.
更多参考：http://download.csdn.net/detail/changyanmanman/7330013