With his repeated off court problem (I know Chandler got caught once, too), I doubt the Spurs would trade for Rush. At least at this juncture.
Why would the Pacers make that trade? I understand he's somewhat fallen out of favor or worn out his welcome and they have a glut of wings, but he's still young, is a decent player and is inexpensive. Why trade him for three fringe players? Let's face it, it would likely take the 1st round pick to get it done.
If the Spurs view him or someone in that class (Chandler, etc.) as the potential missing piece and as a useful piece going forward, then they should surrender their 1st. This team has four young, talented players now, they'd be acquiring a fifth in the trade and right now, it's more important to improve their chances at winning one last championship in the Duncan era, then holding out hope of landing a decent prospect picking 20-25. People get so caught up in 1st round picks a lot of the time, but in reality, picking where the Spurs are likely to be picking, you're just hoping to get a player like Chandler or Rush. Only, they've already got some experience and don't need to be developed as much.