The Jaguars vs. Eagles matchup is one of several games scheduled for London next year. The Seattle Seahawks and (soon to be) Las Vegas Raiders as well as the Los Angeles Chargers and Tennessee Titans will be two others expected to play. The NFL has a deal with the Premier League’s Tottenham Hotspur to hold at least two games at their new stadium in Northumberland Park starting in 2018.
While an Eagles game in Jacksonville would have probably garnered a prime time spot (likely Sunday Night Football) there are other home matchups that will get national notoriety. The team is hosting the Pittsburgh Steelers, New England Patriots, and Houston Texans next year, so multiple nationally televised games (in addition to this London game) is still very likely.
UPDATE: The NFL is announcing the Jaguars vs. Eagles game will either be Week 7 or Week 8. It’s scheduled for Week 7 right now, but that could move a week later due to scheduling concerns.