Apart from some bug fixing, if necessary, I don't plan to do any further work on XGM 3, so version 3.6.13 will probably be the last release for that branch. What I plan to do next is a series of XGM beta releases incorporating some of the new features like loyalty, and hopefully politics/religion.
XGM version 4.0.0b
Here is what I plan to do for the first beta release.
(1) Drop support for the vanilla map.
(2) Switch to version 3 of the Mundus Magnus map.
(3) Convert the Brutii into the Independent City Sates.
(4) Introduce loyalty for the GCS.
The Independent City Sates
This faction will be a rebel faction for the Greek City States, allowing for the introduction of loyalty for the GCS. The unit roster will be exactly the same as the GCS, and apart from differences in the map and banner colours I expect that all the artwork, including unit skins, will be exactly the same. The faction will not be playable, mostly because playing a shadowing faction causes CTDs under certain circumstances, but also because it would be just like playing an easier version of the GCS.
The new campaign will be based on the current Unified Rome campaign. Pyrrhus of Epirus will be the faction leader, although there will be "sub-faction" leaders for a number of other important City sates, just like the current set up in the GCS. The stating regions will include Syracuse, Southern Italy, Epirus, Crete, Halicarnarsus, Byzantium and Nicomedia, Chersonesus, Massilia, and Emporion. It won't include Cyrenaica because that will eventually go a rebel faction for the Ptolemies.
These are just tentative plans, so feel free to make suggestions.