Why would you not dump Dunn at the deadline for some decent SP prospects? This season is over. It's about the future at this point.
You'd still have a chance to re-sign him in the off-season.
The only thing I can agree with you on is the oppurtunity to resign him in the Off-Season... I wouldn't trade him though unless he could somehow get in a haul similar to what UMD stated. He's our best offensive producer right now, why risk losing him for good? We don't have a 1b option. Having to play Morse, Bernadina, and Morgan everyday would be like going back to '08 when we had Orr, Kasto and Langerhans playing. Yes the first three are better, but its like conceding. We are 5 under .500. Nothing completely hard to do. The Braves did it last month and are now 10 above .500. I don't want to lose more offense just to gain more pitching when we haven't even seen the likes of Detwiler, Zimmermann, and Wang. (let alone made any offers for any other veteran pitcher)