The Eagles will lose Bradberry (2nd team All pro), probably Hargrave (played at an pro level) CJGJ, Edwards, Cox, and Miles Sanders. Kelce and BG might retire too. So they will lose alot, but I do agree with your point. The NFC as of now is down and potentially having a 24 year MVP caliber quarterback who will only improve means they should be in a position to make the playoffs and maybe the Super Bowl year in and year out. All the quarterbacks currently are in the AFC.
I think Detroit is going to be good, maybe not so much next year but the years following. The Giants have Daboll, so I expect them to keep on getting better. But the NFL changes so fast. In December of 2015 the Eagles sacked Chip and were in disarray, 26 months later they won the Super Bowl. Same with two years ago. They won 4 games and hired a guy who we all thought was clueless. So much can change in a short time.