One thing that was the best feature of Nexus is that it was always completely clear that it is Google Android, without custom skins. Another virtue of Nexus is its reasonable price and availability for the mainstream public. Lead role of this line is that it sets the standards. It is also used to indicate how Android works, and to influence other producers of smartphones to step up the game and raise it to the next level.
Another reason against of revoking the line is that Google needs it to practice and develop Android. Engineers need a chance to apply their knowledge in practice, especially on the device that they can use, and see what works and what does not.
At this point, anything can happen. If Google decides to kill off the Nexus, it will surely be a great loss for the smartphone community.