Run defense will improve, that's pretty much a certainty. I have little concern for our run defense next season.
This defense is going to surprise a lot of people. We already garner a lot of turnovers, if we actually get a pass rush, we'll lead the league.
I think people forget our offense is pretty good. Another year of OL cohesion, Collins addition, and WR's learning the craft, and we're primed to score 30ppg. Teams aren't going to score 30 points against us running the ball.
A pass rush and an affinity for forcing turnovers forms a harmonious couple with our offense, and I believe there are a few guys here more than willing to provide the stat that passing efficiency differential is the #1 correlation to winning in the NFL.
I don't really care about rushing defense, to be honest. A top 15 unit in YPA and top 10 in yards allowed (less attempts) is fine with me.
You also keep the other team out of the RedZone by rushing the passer well. Sacks, quite often, are drive killers. I'll take a drive killer over an efficient run defense pretty much any day of the week.