Also check out the wiki version of this post.
The most notable new features in this release are tag extension support for all the Maps parser functions, more consistent error handling via Validator 0.4 and compatibility with the upcoming MediaWiki 1.17. Most changes are internal improvements, but there are also several bug fixes and minor new features.
There only big new feature on the roadmap for 0.7.x is the infamous images-as-layers one. This feature was supported by the now long obsolete Semantic Layers extension (example), and has been requested by dozens of people since the first releases of Maps. Next to fixing the bugs that show up, the focus will mainly be on adding new functionality. Feel free to propose new features, or help out creating them.