In Cubase 9 the Key Command has been added.
The track needs to be highlighted. Then use the key command, and the background behind the track names turns blue, type in the new name, and press tab to go to the next track.
Or, you can double click instead of using the key command.
The key command is in Edit>rename first selected track
There is also a new KC for Edit>edit info line to do the same with the info line.