Recently read an article over on NFL.com reasoning that a later trade deadline would be more apt to generating more trades and that you simply have to look at the MLB and NBA for proof. I'm not so sure. See, unlike the other major sports, the NFL trade scene is hamstrung by its vast array of complicated schemes and playbooks; you can't just plug Random Good Player into your lineup and expect immediate positive results. Sure, you would much rather have Sam Bradford or Ryan Tannehill throwing to Dwane Bowe, but it takes time for any player to learn the playbook and then be able to execute it in sync with the rest of the team. While he's in the process of doing that, he could actually be more of a detriment to his team than an asset.
Case in point: Carson Palmer came on board for the Raiders a little more than a quarter of the way through last season. He threw six interceptions in his first six quarters of play. Comparatively, he threw nine in the next 32. This year, despite a new offense and new head coach, he's got five in 28 quarters of play. Time to learn and time to practice with your team mates can make a big difference.
Of course, Palmer is not one of the all-time greats. But he was obviously a significant upgrade over a player such as Gradkowski, the QB he replaced. Yet we can clearly see it takes time for even a good player to be able to utilize his skill set in conjunction with the scheme and plays being run by their new team. This creates an unfortunate environment where trading is largely nonconducive. There are simply a lot more things that have to factor into trades in the NFL and I don't believe an extra few weeks is really going to change much. If the NFL really wants to increase trading, they are going to have to provide incentives to make it more appealing.