It takes time to develop rivalries and your biggest rivals are those teams, usually from your own division, that you find yourself with most often in important games (games played for a division title or playoff berth). Often times, your biggest rival is the team that beats you in those games more often than you beat them. Ask titans fans who their biggest rival is (at least was) and many of them will say the Ravens. Why? Because the Ravens beat them in a couple of very big games in recent years. They may start to develop the same "envy/hate" attitude toward Indy unless they can start beating them again.
As far as the Texans, it's too early to tell, but the Tennessee thing is big for many for obvious reasons. It's the team most Texans fans dearly want to beat. But it's more of a one-way rivalry (until we can start beating them in important games and getting them to hate us as well). Same with Indy. There's nothing there yet for the Texans in terms of rivalry - other than two losses per year. If there's been a rivalry in these first two seasons, it would have to be Jax since we were fighting with them to stay out of last place.
I see the AFC South changing a little in the coming years and there will likely be a more heated race between all four teams instead of just two. That's when some real rivalries will emerge.
As far as Dallas, your most heated or hated rival can't be a team that you play only once every four years.