The Eagles will clinch the #2 seed in the NFC and a first round bye if they beat the Cowboys on Sunday. You had to know that this Eagles-Cowboys matchup the final weekend of the season would be meaningful, and it is for both teams.
Because the Vikings lost last night, the Eagles and Vikings now have identical records. The Eagles hold the tiebreaker over the Vikings with the better conference record, and thus control their own destiny for that #2 seed. However, the Eagles can drop completely out of that spot, and drop to as low as the #6 seed if they lose to the Cowboys possibly. The Eagles have a lot to gain from a win this weekend, and unfortunately, they have a lot to lose. In fact, the Cowboys who sit at #6 in the NFC right now, could still end up with the #2 seed and a first round bye. If the Eagles, Vikings, and Cardinals lose, and Cowboys win, they take the #2 seed, and the Eagles will fall to the 5th or 6th seed.
If the Eagles lose to the Cowboys, and the Vikings and Cardinals both win, the Eagles would be the #5 seed, and would travel right back to Dallas for a first round playoff matchup. If the Eagles lose to the Cowboys, and the Vikings win, and the Cardinals lose, the Packers also jump the Eagles, and the Eagles drop to the #6 seed. In this scenario, the Eagles would also travel back to Dallas to play the Cowboys. There are also scenarios where the Eagles could lose, drop to the #5 or #6 seed and play the Vikings, if the Vikings lose their game, and Cardinals win.
So, a win would be huge for multiple reasons as you can see. You do not want to have to play in Dallas twice in a row, and in my opinion, you never want to play a divisional opponent for the 3rd time of the season in the playoffs. Should be a very interesting weekend.