Sort of...
While DDR4 DRAM has the potential to be twice as fast as DDR3, it isn't currently and isn't likely to be for years to come. In addition DDR4 uses point-to-point topology which is not desirable for most people because if makes adding DRAM impossible and an upgrade a very costly experience as all of the DRAM must be replaced. DDR4 is also going to be considerably more expensive than DDR3.
At the moment DDR4's primary market is servers as it doesn't offer any performance advantage for typical desktop use where DDR3 is far from being a system bottleneck. Potential doesn't = reality at this point in the DRAM game.