Considering the amount of future picks in the Spurs' power, I don't see this as a necessarily bad thing. It's the famous "churn" that rebuilding teams go through; the Thunder also dropped a promising player or two last season due to roster crunch, and will likely do the same in the coming years.
Whoever's worth the minutes should rise above their peers in practices and in making use of their playing time. As they say, "the cream rises to the top". The increased compe ion over minutes/roster spots could end up being a good thing, even - I remember many posters complaining about Sochan being "handed" the starting spot due to lack of compe ion, for example, and this would be the opposite.
If Branham or Wesley end up reaching their ceiling on the Pacers or Pistons, I doubt the Spurs will lose much sleep over it... The true keepers tend to show their worth early on in the NBA.