When buying on eBay, be careful!!
First, you have to get the correct DVD for your "generation" of the software. You cannot upgrade your system software through just a DVD. Be sure to shop by model year of your 4Runner.
Second, be sure you get an "Update Disc", as that will update the maps. A "Program Disc" is the disc that comes with it from the factory, and you don't want that if you're looking to update your system. Program Discs wind up on eBay when people try to get money for their old discs that are being replaced!
And yes, Toyota has sometimes had issues with releasing updates on a regular schedule. They were really bad at first, but I thought they seemed to be getting better lately.