Back when Microsoft announce their new Windows 10 os, they also announce that they will be rolling out the Windows 10 update for the Lumia 900 but they later announce that they have decided not to do it.
Not getting the new Windows 10 update when they were expecting to was bad but the fact that the Windows 8 that it was running on was buggy and frustrating to use made it even worse for the users. Some users are reported that some of the apps were taken out from the Lumia 900 and in the end, a lot of their users had to give up on the Lumia 900.
While we are not sure when Microsoft will come out with a new OS to replace the Windows 10 OS, many believe that the same thing will happen to the Microsoft Lumia 950 when the time comes.