I've said already that there's no reason to sell low... Manu's skill level could still be very high (though I disagree it will ever be superstar level again, he won't get the minutes nor touches even if his body allowed), and his expiring is large.. he's worth more, perhaps even a lot more, than he should be - because of that unique combination.
That said, Tyrus Thomas and Salmons is a trade I wouldn't do... good players, I think, don't get me wrong. Thomas is too slow BBiq wise, despite his athletic prowess. He is one who just couldn't have the type of defensive stamp we need right now.. and a strong defender is something I wouldn't label Salmons. Beside, I think this is one of the times when you can trade an offensive player like Ginobili for strong defenders who lack offensive games, because we have enough offense to supplement them as long as we are holding teams below 90...
I don't have any trade ideas myself, because I'm not in the Spurs FO and I essentially don't watch other teams or know much about the CBA, admittedly. Yet I would be very surprised if there aren't fairly attractive offers for Manu on the table right now, just not good enough for the wary/smart FO to jump on.
I would be surprised if they traded Manu, period. I'm not sure why they would trade him for another perimeter scorer though, since we have an overload of those..