If Tyranitar is still in after 5 consecutive turns, then it's probably already sweeping the opponent's team.
Tyranitar wasn't just used for Sand Stream you know. Hell, the nerf might actually be good on some teams that don't want their other Pokemon to be buffeted constantly. Ttar will likely remain a threat because Ttar is awesome. It has STAB pursuit, decent offensive typing, huge stats and a plethora of options. Sand Stream is just icing on the cake; 5 turns of icing no less.
I've actually been considering this so far; before this Gen I loved T-Tar, and still do; back in fourth I ran a devastating Sand team (Tar, Scizor, Spiritomb, Gengar, Cradily, Forretress, if anyone can remember fourth Gen's meta so well), and as such was thoroughly sick of Sandstorm in fifth, but at that point was reluctant to be running Tar on a team that lost more than it benefited from the sand. Now, what he lost in the ability to set up a whole play style and quite badly over-centralise the weather war, he gained in splashability; he's much more useable on a variety of teams that can use his defensive presence in the sand early on, or use him late-game to clean up, without having to worry about buffeting Life-orbers and walls that don't like the residual HP loss.