Here is what seems really interesting about that to me:
Season - number of teams averaging >100ppg
1999-2000 - 7
2000-2001 - 4
2001-2002 - 4
2002-2003 - 4
2003-2004 - 2
2004-2005 - 6
2005-2006 - 5
2006-2007 - 9
2007-2008 - 13
2008-2009 - 13
2009-2010 - 18
2010-2011 - 11
2011-2012 - 3
2012-2013 - 11
(I would say that 11-12 can be disregarded due to the lockout).
Overall scoring is up, but fewer players are putting up high numbers regularly.