The key words here are "under this scenario." Yes, indeed, if all those variables come into play, Bellinelli could indeed get traded at the deadline. But it's not going to happen for the following reasons:
1. Anderson will not supplant Bellinelli in the rotation. There is simply no way Pop would play an unproven rookie over a reliable veteran and 3-pt shooting champion. That would probably make the Spurs a worse basketball team as well.
2. And if he were to be supplanted by Anderson, then there would be absolutely no way a team would give up a first round pick to acquire him, unless they also get attractive assets in return (i.e. rights to Davis Bertans).