We are still waiting to publish the stable version because currently the GRASS drivers (XDRIVER, HTMLMAP, PNGdriver, CELLdriver) face a major rewrite and cleanup. We want these essential drivers to be working properly on most platforms. This cleanup is considered to be the last change before publishing GRASS GIS 5.0.0.
Sorry to say, we cannot provide a timeline (yet), but the team is working hard on the remaining problems. There will be a pre-stable release which needs to be published and widely tested. This pre-release should be rather identical to the final stable release, only addressing unknown install problems. Please keep in mind that GRASS operates on many platforms which can be a technical challenge sometimes.
To find out what's been done since the last publish, read our "News" page.
Working on a reliable open source GIS for you,
GRASS Development Team