The last time the Eagles started the 3-0? That was back in 2004 when the team finished with a 13-3 regular season record and advanced to Super Bowl XXXIX where they lost to the New England Patriots. Philadelphia did not suffer their first loss until Week 9 against the Pittsburgh Steelers that year.
Since 1990, 75.2% (91/121) of NFL teams that have gone 3-0 through the first three weeks of the season have made the playoffs. Compare that to teams that have gone 2-1 at 52.8% (132/250), 1-2 at 25.3% (62/245), and 0-3 at 2.5% (3/121).
The Eagles are clearly in a favorable position. They have started the season off strong and they sit at the top of an NFC East division that does not appear to be overly challenging.