I don't think MS has any intention whatsoever of getting rid of Access. They may transform it into more of an end-user tool than a programmer's tool, but it is never going away. The forking of the Jet database engine into the traditional Jet 4 version that ships with every copy of Windows (because Active Directory uses Jet 4 as its data store) and the version that is owned by the Access development group (the ACE, with its ACCDB file format, which is, de facto, Jet 4.5 or maybe Jet 5).
Access is a hugely popular and useful application and functions in a whole host of levels within any number of organizations, large and small.
Why is there no open-source alternative to Access?
Because it's way too hard to create such a complex piece of software that does so many different things well.