Mass Effect 4 is currently in production and it will be coming out with a brand new plot and protagonist. The other thing that will be very new to the series is the online feature.
Bioware has already confirmed that Mass Effect 4 will come with an online gameplay. While the game developer has yet to give us the details about it, we already know that the feature is going to come as a separate online mode.
This is pretty obvious since Dragon Age Inquisition saw the addition of such a mode. Also, considering that both the Mass Effect series and Dragon Age series share a lot of similarities, there is no doubt that the online mode in Mass Effect 4 is going to be identical to Dragon Age Inquisition.
If you really require a confirmation on Bioware on this, you can wait another week for E3. After all, Bioware is expected to unveil Mass Effect 4 and spill more beans on the game at the upcoming event.