There isn't yet a firm release plan for when Inkscape 0.91 will be officially introduced but there is this documentation in working towards the next release. A lot of features have been added and many bugs fixed (over 700 bug-fixes for Inkscape 0.91) but they aren't yet in a code freeze for this next milestone.
A full listing of all the additions for Inkscape 0.91 can be found via the Inkscape release notes on their Wiki. Among the major changes for Inkscape 0.91 are OpenMP multi-threading for all filters, C++ code conversion, Cairo rendering for display and PNG exporting, major improvements to the Inkscape tools, usability improvements, a native Windows 64-bit build, rendering fixes, and much more. Inkscape 0.91 features a new renderer based upon Cairo that's been in development for the past few years and is significantly faster for most drawings, the OpenMP multi-threading for filters will be a huge speed-up on multi-core systems, there's big savings in memory usage, the program is much more responsive, and there's other optimizations with regards to its renderer.
While the Inkscape release notes on the Wiki are very thorough, for those wishing to learn more about Inkscape 0.91, can read about many of the prominent 0.91 features via the Inkscape Tutorials blog. That's the news today with this Inkscape blog writing at length in the past few days about many of the new features, and there's many screenshots within these blog posts describing the new features and functionality. It's worthwhile to checkout for anyone interested in this vector graphics editor.
More information on Inkscape itself is always available via Inkscape.org.