Here is a quote from FamilySearch that gives a little more information about this subject:
GEDCOM X is a specification for an open data model and an open serialization format to support genealogical data communications. The FamilySearch Family Tree API is built on this specification.
The world has used GEDCOM as a standard to exchange family data for many years. The problem with GEDCOM is that even though it has become a defacto standard, there is data loss as files are passed between systems that have differing features and supported options. The problem grows even deeper as the world picks up pace in building even more family history applications in an online social environment. It is time for a major facelift to the standard.
In addition to text-based lineage-linked data, GEDCOM X is capable of preserving rich media content in a new file format that will offer high-fidelity preservation of records. But more than that, we live in a connected world, and we need a common protocol to communicate family data between cloud systems and apps. This is what GEDCOM X is all about. It is currently being developed by FamilySearch in cooperation with many genealogy and technical experts.We haven't heard a lot about this lately. But at RootsTech 2013 it was the topic of conversation in several areas and discussion panels. GEDCOM X was introduced at RootsTech 2012. See Glimpses of GEDCOM X by Randy Seaver.
There are other organizations working on essentially the same issue; genealogical data transfer standards. For example, I have written in the past about BetterGEDCOM and The Family History Standards Organisation (FHISO).
It looks like there might be some news in this area. Keep tuned.