I think it's time and I believe the Rams want to hire a DC that coaches similar to Sean McVay. If the Falcons part ways with Dan Quinn, I believe Quinn will be on the short list and I don't care about 3-4 vs 4-3 DC's coach to their personnel and defenses have different packages on every down, plus I like the 4-3 better. but you adapt to your personnel like with the New York Jets, who currently are coached by Gregg Williams a 4-3 running a 3-4 because of personnel it can happen and here are the teams currently running a 3-4 the Green Bay Packers, Los Angeles Rams, Pittsburgh Steelers, Baltimore Ravens, New York Giants, New York Jets, Washington Redskins, Carolina Panthers, Miami Dolphins, Tampa Bay Buccaneers, Denver Broncos, Tennessee Titans, Houston Texans, Chicago Bears, and the Arizona Cardinals.
Again some have mentioned John Pagano, currently with Houston, however, I see a younger type of coach and I know how highly McVay thinks of Dan Quinn and believe if the Falcons do make a change, that Quinn would be on many people's short list and coaching with McVay and the best defensive player in football might be a good match IMHO.