I dont think we still need blu-ray disks for games since even if the game needs 4 DVD disks or 2 double-layered DVD's,you install the game, then you dont have to use all the DVD's again instead you only need the 1st one to start the game (or none depending on the game) so Blu-Ray's are still not necesary,i believe that only when the developers need more than 2 double-layered DVD's, then time will be right to replace DVD's with Blu-Ray discs but now it would only be an extra cost.
On the other hand,BD discs are a great replacement for DVD when watching videos/movies(especially if they are HD),thats because movies do not need to be installed,you just instert them and click play(with the exception if you bought them online,then you need to store them on your hard drive).So BD discs are great for watching movies especially if they are long and HD,nobody wants to watch movies in parts