So last night's small tragedy - Phils lose, Mets and Brewers win - has tightened things up somewhat.
Remaining schedules for all teams (all home games):
PHI: 1 vs. Atlanta, 3 vs. Washington
NYM: 2 vs Chicago, 3 vs. Florida
MIL: 2 vs. Pittsburgh, 3 vs. Chicago
IF Phillies go 4-0:
Win division outright, first round home field advantage vs. NL West champion or Wild Card Milwaukee Brewers.
IF Phillies go 3-1:
Clinch playoff spot; Mets take division (on regular season record tiebreaker) if they go 5-0 in remaining games, and Phillies play Cubs in first round.
IF Phillies go 2-2:
Mets win division outright with 5-0 or 4-1 finish. Three way tie for all three teams if Mets go 4-1 and Brewers go 5-0 (NL East regular season tiebreaker favoring the Mets tiebreaker only comes into play if both teams are guaranteed a playoff spot). One game playoff between Mets and Phillies for NL East title (in Philadelphia), and loser plays Milwaukee for one game to determine Wild Card.
Phillies clinch playoff berth with one Milwaukee loss.
IF Phillies go 1-3:
Mets win division outright with 5-0, 4-1, or 3-2 finish (barring three-way tie with Milwaukee). Three way tie scenario if Mets go 3-2 and Brewers go 4-1. Milwaukee claims Wild Card with 5-0 finish; tie Phillies with 4-1 finish, one game playoff in Philadelphia.
IF Phillies go 0-4:
Mets win division outright with 5-0, 4-1, 3-2, or 2-3 finish (barring three-way tie with Milwaukee). Three way tie scenario if Mets go 2-3 and Brewers go 3-2. Milwaukee claims Wild Card with 5-0 or 4-1 finish; tie Phillies with 3-2 finish, one game playoff in Philadelphia.
Clearly the scenarios above strongly favor the Phillies, but a final week collapse is far from impossible (Cleveland Indians in 2005 - 1-6 over final seven games, lost playoff spot; New York Mets in 2007). Also important to keep in mind -- while both Milwaukee and New York have multiple games remaining against Chicago, it's a Cubs team more interested in preparing for the playoffs than winning baseball games (having clinched best record/ homefield advantage). Expect them to be playing to win, but at something less than full strength.
SIMPLE SOLUTION: Just win baseball games.