With the signing of Pendergraph, I'd say the Spurs will leave that last roster spot open to review the players from the summer league. If Thomas impresses, he could probably be signed. But I think the Spurs leave that spot open for a 'just in case' situation, somebody being released from another team, player buyouts, etc.
I'm great at multi-tasking -- I can waste time, be unproductive, and procrastinate all at once. Ain't life grand!!