First, Small SAMPLE SIZE
Second here's just the Exapansion teams from the great improve/decline post over at Climbing the Ladder
1998 - Chicago - -0.438 PPM
1998 - Miami - +0.668 PPM
2005 - Chivas - +0.375 PPM
2005 - Salt Lake - -0.375 PPM
2007 - Toronto - -0.733 PPM
2008 - San Jose - +0.600
2009 - Seattle - ?
Does this mean that Seattle is in line for a bump? Again, sample size makes this moot.
But on average MLS teams tend to win more points in the second half than the first (fewer ties?) and the previous 6 expansion teams barely did better in the second half. IF Sounders follow either path they would be a 48 point winner this year.