support for ltree

I am wondering if the contributed module <ltree> will always be part of
Postgres? Do contributed modules ever get absorbed into Postgres itself?

The reason I am asking is that, although ltree seems to have been a
contributed module since at least 8.3, how can one know if it will always
be part of subsequent versions of Postgres?

Are there any plans to make <ltree> a built-in datatype, like <json>,
o<xml>, or the various Geometric Types (eg, <polygon>)?

Michael Shapiro
Senior Systems Engineer
National Center for Supercomputing Applications (NCSA)
University of Illinois, Urbana-Champaign (UIUC)