Never seen anything, and given how crap google maps on BB is I suspect there's nothing in the pipeline.
You might be better off looking at the native maps, or have a look through some of the threads in here as there was a reply to one of mine where someone here gave a good mapping app which may work off-line.
You can cache a certain area of the maps by looking at it while you're online - be sure to zoom into the level you wish you use once you're offline and scroll around to everything you want to see. Don't close the app or reboot the bb etc and the maps will stay in the cache for you to see while you're offline. Only the level(s) you zoomed into while you were online will work offline - zooming out doesn't even work because it tries to redraw and scale everything appropriately
Its not the most efficient way to do it, and you loose everything if you restart the app, but it works to get you through in a pinch.