Swingman rotation (as of now):
2 Ginobili
2 Mason
2/3 Udoka
3 Bowen
There's one spot left for the active roster in this rotation.
Barry and
Finley shot the ball quite well in SA.
Mason shot just a hair shy of 40% on 300+ 3-point FG attempts last season, so there's hope, but I think the Spurs could use another swingman who can really shoot the 3. Before last season I'd say that
Matt Barnes might be that player (really wouldn't complain if the Spurs could pick him up).
Other potential candidates:
Ricky Davis - has been a prolific and accurate shooter for the Heat over the last two seasons, shooting 40% on 643 3-point FG attempts during that time. Of course, he probably is seeking too much $ over too many years and he doesn't necessarily fit the profile of the 'prototypical Spur.'
Gordan Giricek - a career 36.8% 3 point shooter, though he's never really been a volume shooter in his career (most 3 point attempts in one season: 119). Reportedly has a large offer from a European club.
Maurice Evans - shot the 3 well last season (39.6% on 202 attempts). Nice athleticism to boot.
Bostjan Nachbar - would be an ok fit, but seems to be looking for more $ and years than the Spurs are willing to commit.
Kirk Snyder - shot the ball well in his first two NBA seasons, but he's been abysmal in limited minutes during the next two.
Casey Jacobsen - shot the ball rather well from 3 in his first 3 NBA seasons before heading to the continent to play for Tau (

) and then in Germany. Last season with the Grizz he wasn't too hot in limited minutes.
I think someone like Evans would fit in well with where the Spurs are headed. I could see Davis if the Spurs wanted someone who can score and shoot the 3 in a fair number of minutes to help rest Ginobili during the season.