I don't expect a championship this year, like I used to in many previous years. However, I think it's within the realm of possibility, and that's more than blind optimism and homerism. The Spurs still have a ton of talent, and at least three players easily capable of making the All-Star team this year. Not many teams can say that.
That said, the Spurs will need a lot of good breaks, aligning of the stars, and flat out luck to win it this year. They need inspired performances by half their roster, and solid performances from the other half. They need an improvement in both individual and team defense that many doubt they have the personnel to accomplish. They need better chemistry than you would ordinarily expect given the amount of time many of the players have been together.
If it sounds like a tall task, a long shot, that's because it is. But the Spurs are one of about 5-10 teams that have the talent, potential, coaching, and veteran leadership that a championship team needs. The other 20-25 teams would love to be in that situation.
....Now if only the season would start so we can all enjoy it.