There are a variety of ways we end up the #2 seed but the main thrust is we probably need to win out, and SF needs to lose an additional game, which gets us a divisional crown and makes us eligible for #1 through #4 and a home game to start the playoffs.
(Essentially SF is two games ahead of us, with three to play, but we play each other. I suppose we could win vs SF and one other, and SF could lose out, but that seems unlikely as a way to win the West.)
As an example, if Chicago ended up taking the North, and we were tied with them, and we were West champions, we'd win that tiebreaker based on head to head.
Other thoughts: No way the Cowboys are the #4. Either the Giants or Redskins will win that division, and everyone else in the East is probably out of the playoffs entirely.
I could see us as the 2 seed but don't see it terribly likely, too many things have to go right. I do see us as the 5 seed going to the 4 and winning on the road, given how weak the East is, and if we got to go to Atlanta in the next round, I like our chances there, too.