Consider the Eagles' roster in Week 1 of the 2018 season. If what we heard on Wednesday is true, that will be their first or second season with Carson Wentz* as their starting quarterback.
Between now and then, as it stands right now, the Eagles can count on one first round draft pick (2018), one second round draft pick (2017), and two third round draft picks (2016 and 2018) that it can use to add talent to its current roster. In other words, as it stands right now, the Eagles will have four chances to pick four players from the top 300 or so college players who will enter the draft between now and the start of the 2018 season. Between now and then, they will need to find players at two of the game's most expensive/least abundant positions: a left tackle to replace Jason Peters, and at least one cornerback to replace Nolan Carroll (who will be 32 years old in September of 2018). In all likelihood, they will find themselves in need of at least one pass rusher to replace Connor Barwin (32 in 2018) or Brandon Graham (31).
Those are just the positions that will clearly be glaring liabilities at some point before Week 1 of 2018. Once you start to consider the other positions at which the Eagles currently have no clear long-term solution -- a second wide receiver to complement Jordan Matthews, an outside linebacker, a guard, the entire depth chart at running back -- along with the ones that could become liabilities by that point (center Jason Kelce and safety Malcolm Jenkins will be 31 and 32), along with the young talent flow required to provide depth at each position, you eventually reach a point where you run out of draft picks or salary cap dollars that might address them all.
Even if Nelson Agholor turns into Antonio Brown and Eric Rowe turns into Josh Norman and Nigel Bradham becomes a player he hasn't been thus far in his career, it still isn't clear that the Eagles will have a capacity to surround their 2018 quarterback with Super Bowl-caliber talent. And that's just from a volume standpoint. We haven't even begun to account for the fact that they might not hit on all four of those draft picks in the first three rounds. Each miss there will be one more player the Eagles need to find in the fourth round or later, or in free agency. Oh, and that's all independent from the question of whether Wentz actually reaches his potential and becomes one of the game's elite quarterbacks.
On Wednesday, Howie Roseman did his best to justify the Eagles' spending of $40 million in salary cap space and five draft picks (two firsts, a second, two thirds for Wentz, a second for Bradford, although if you want to write off the latter as a sunk cost, the point remains). But the reality is that a franchise quarterback alone does not guarantee sustained success. Are the Colts any closer to the Super Bowl now than they were in Andrew Luck's first year as a starter? Are the Falcons any closer to the Super Bowl now than they were in Matt Ryan's first season as a starter? Are the Chargers any closer to the Super Bowl now than they were in Phillip Rivers' first season?
The year Aaron Rodgers won his only Super Bowl, he had a wide receiver who had been drafted in the second round four years earlier (Greg Jennings), a tight end and wide receiver who had been drafted in the second and third rounds two years earlier (Jordy Nelson and Jermichael Finley), a guard who had been drafted in the second round four years earlier (Daryn Colledge), and a right tackle who had been drafted in the first round that same year (Bryan Bulaga). On defense, those Packers had a nose tackle and a linebacker who were drafted in the first round the previous year (B.J. Raji and Clay Matthews, Raji at No. 9 overall), another linebacker drafted No. 6 overall four years earlier, and a free safety drafted in the second round five years earlier (Nick Collins). All told, the 2010 Packers had seven starters whom they selected in the first or second rounds in the five years AFTER they selected Rodgers at No. 24 overall in 2005.
Look at that from another perspective. The Eagles traded up to select Wentz. In a best case scenario, he becomes one of the greatest quarterbacks of all-time, as Rodgers did. In that scenario, all of us would agree the deal will look like a smart one, just like we'd all agree that the Packers would have been justified in trading a similar package for the right to select Rodgers. But look at that 2010 Packers team from the perspective of the Eagles five years from now: they would be without a starting linebacker (Hawk), free safety (Collins) and running back (Brandon Jackson), all of whom were added with picks that the Eagles do not currently possess. That's still a very good team, arguably even Super Bowl caliber. But that's also an extreme example: one of the greatest quarterbacks of all time playing for an organization that stockpiled early draft picks and had an unparalleled success rate with those picks.
You can point to any of a number of factuals and counter-factuals to justify Wednesday's deal. Nobody will complain if the Wentz era in Philadelphia is similar to the Rodgers era in Green Bay. Eli Manning won a Super Bowl for a team that traded a ton of picks in order to select him. Joe Flacco and Steve McNair were/are both solid starting quarterbacks from the I-AA ranks who led their teams to Super Bowl berths.