Is a shame AMD chose this naming scheme, because undedicated people (In terms of PC) might not understand at first. Although I'm sure even those guys will pick it up after launch.
For most of us here who are more informed, we can see that the flagship is in fact the Fury X and Fury Pro being the second down, meaning that the 390X is the third down, exactly the same has happened with previous generations.
I.e GTX 680 becoming GTX 770 , and HD 7970 becoming R9 280.
GTX 680 > GTX 770
GTX 780 << New flagship (At launch, before 780 Ti came along)
GTX 770
HD 7970 > R9 280
R9 290X << New flagship
R9 290
R9 280
R9 290X > R9 390X
Fury X << New flagship
Fury Pro
R9 390X
Maybe somebody should put out an illustration, to make it simple for the uninformed to understand.
The original titan was the flagship iirc when 780 was launched, Faster more vram, 780 was a cheap and still fast version