Luckily, the Spurs are taking steps in the right direction regardless of a trade. Settling on one of Finley or Barry will make this team better. Getting Bonner on the floor more will make this team better. More Parker and perhaps more Duncan and Manu will make this team better.
The gulf between the Spurs and the Mavs isn't so big that the Spurs MUST get help from an outside source. If they alter the rotations and the way they play, I think they can catch back up.
But they'd need to be major changes ... and this articles cites pretty major changes. Going younger (Bonner over Horry) and eliminating Finley or Barry from the rotation is a drastic step for this team.
But a good one.