The GEDCOM format looks like a databasing format from the 1980s. Why hasn't a more updated format emerged?
The problems with the GEDCOM formats and attempts at its extension are myriad.
The GEDCOM format assumes all people will have a surname or a Europeanized name.
The GEDCOM format assumes that the general structure of a family is linear and a tree when family trees are generally actually family graphs with a degree of intermarriage, bastardy, and interbreeding.
The GEDCOM format is difficult to verify and lacks simple consistency checking mechanisms and as such allows the formation and propagation of computationally ambiguous loops like grandfather paradoxes.
The GEDCOM does not distinguish between conflicting degrees of information such as sourced entries vs non-sourced enteries. The format does not lend itself to amendment of properties or the extension of data by the linking of further sources.
The GEDCOM location data does not capture the changes of the name of locations throughout history; place names are regularly given in strictly modern terms that don't make sense within the context of the historic areas that people originate. Example: ancestors being listed as living in Connecticut or Vermont, USA in 1750. GPS coordinates are generally better for the purposes of dereferencing ahistorical location data to digital maps. GEDCOM then does not properly correlate location data of sourced events to graphical areas on maps.
Frequently webpages and sites dealing with large family graphs do not deal well with the importation of 5000+ entries and the fragmentation of the import data is difficult because the linear and singule file nature of the GEDCOM format. The unit document of genealogical data is the collectively documented properties of a person through out their life; uploading needs to be constructed from the premise of importing and updating members of a family graph rather than in terms of uploading entire family trees and verifying each and every entry by hand. In otherwords, the better format is a distributed source versioning repository.
All of these problems are solved in the contemporary programming and developing domain of package management and source code development software.
Open document containment and management formats that would be appropriate for incorporation to construct a new genealogy format or what I call a family graphing format include zip, 7z, or tar.gz.
Github is functional for a distributed source version repository, and the format of GitHub can be extended to a genealogy specific distributed development environment. Say GenGraph.
Semantic web technologies would be really useful for automatically finding and retrieving source documents; I don't see technologically why pages on a modern wiki can't be partially constructed from existing documented and semantically marked up sources like the Wikimedia commons or DBPedia, so biographies might be imported at least for notable individuals. These same technologies would be useful for linking data to systems like Geohack, so events could be displayed in a map frame on their page. And RDF-equivalents would be ideal for linking together collections of genealogical documents, resolving their dependencies, and interfacing them with automated reasoners and compilers to provide data validation and consistency checking systems.