Since 1979, six teams have come home with a 3-2 lead in the World Series and all six have won, with only one of those Series going to game 7 (1997). Nine other teams have returned home trailing 3-2 and seven of the nine have won the Series (exceptions: '92 Braves, '03 Yankees who both lost game 6). Sounds good, right? That's 15 Series, and the team coming home in game 6, whether up 3-2 or down 3-2, is 12-3.
Then again, since the ALCS and NLCS has expanded to seven games, four teams came home with 3-2 series leads and lost: '85 Jays, '91 Pirates, '03 Cubs, and '04 Yankees. Twelve others came home with 3-2 leads and won (including the '98, '00, '03 and '09 Yanks) but four of those went to a game 7 and two of the winners ('92 Braves, '03 Yanks) needed unlikely rallies to win (remember: if the '92 Pirates had a decent closer, they would have won the NL). The key fact in those four series where the leader lost -- only the '03 Cubs ever led at any point in game 6 or 7 (the Royals never trailed the Jays, the Braves blanked the Pirates twice, the Blosax never trailed the '04 Skanks). Total tally: 16 LCS where the team leading 3-2 came home for game 6 and (possibly) 7, home teams are just 8-8 in game 6, 4-4 in game 7. Crapshoot.