Recruiting will naturally shift to look for stronger athletes, mirroring that of D2 and D1. Remember, back in the 90s (so I'm told), a 9:10 guy was one of the top 5 runners in the nation. Glancing at it now, he'd be about 120th. The great thing about D3, and about running in general, is that the 4:30/9:40 guy in high school can become extremely good if he puts his head down and trains for a few years, and in D3, there's always a spot for that athlete. I expect that will stay the same, although the cream of the division will continue to get better. Already, 4:15 milers and 9:10 2-milers are the top recruits in D3, and I expect those times to continue to decrease.
One thing that I think could accelerate the process is the rise of NCAA athletes demanding pay. Obviously that will never happen for non-revenue sports, but I expect within a few years, basketball players and football players at D1 institutions will be paid. D1 schools are already dropping track and field and XC in droves, and where do you think all that money they need to spend on their basketball players will come from? Track at D1 schools may disappear in the near future, meaning that all those D1 caliber athletes might take their talents to D3.