Interesting times ahead. The upcoming MySQL 5.7 promises to provide great enhancements in the spatial space. They've scrapped much of the existing GIS plumbing they have in place seen in prior 5.6 and are replacing muc of it with Boost Geometry. In addition R-Tree indexes will be available for InnoDb. Details: Why Boost.Geometry in MySQL? and Making use of Boost Geometry in MySQL. Along the roadmap (not for 5.7) they plan to have geography support as well and projections, 3D and the various output formats e.g GeoJSON currently available in PostGIS.
Just when I thought database spatial domain was getting boring. It will be interesting to see how the new MySQL Boost Geometry stacks against PostGIS GEOS /3D CGAL support. Might be time for a PostGIS/MySQL shoot-out soon.