RPM is being considered as part of the Linux Standard Base, or LSB, 1.3. This will define a standard packaging format for Linux distributions, and over time reduce the RPM differences between distributions.
In addition, other efforts are underway to help unify the diverse Linux distributions, including the Filesystem Hierarchy Standard and the adoption of RPM by many Linux vendors.
The FHS, or Filesystem Hierarchy Standard, defines the purpose of all the upper-level directories on Linux systems, such as /var and /usr/bin. This standard, along with the Linux Standard Base, or LSB, is driving Linux distributions to a greater degree of similarity.
The FHS helps by specifying where applications should get installed and which directories should be left to local administrators to manage. The FHS also defines the purpose of all Linux directories, giving vendors and application writers a better idea of where they should install their packages.
Cross Reference
See www.linuxbase.org for more on the LSB. See www.pathname.com/fhs/ for more on the FHS.
RPM has been adopted by a large number of Linux distributions. In addition, standardization efforts, both for RPM and for filesystem locations, are making Linux systems less varied.
This means that over time, many of the RPM-related differences between Linux distributions will fade away, making it easier to create cross-platform RPMs.