I think that some of the drop in 2007 was because the FJ Cruiser came out at that time and stole some 4runner sales. It looks like the 5th gen sales never did reach the 4th gen numbers.
What amazes me is Grand Cherokee sales. Much higher.
Calendar Year Grand Cherokee sales
United States
Canada
Outside North America
Total
1993-1998[38]
~2,000,000
1999[39]
300,031
2000
271,723
2001[40]
223,612
2002[41]
224,233
2003
207,479
2004[42]
182,313
2005
213,584
2006[43]
139,148
2007
120,937
2008[44]
73,678
2009[45]
50,328
6,254 [46]
14,869[47]
71,451
2010[48]
84,635
7,255 [46]
91,890
2011[49]
127,744
_________________And Wrangler sales__________________________
2007[23]
119,243
9,834 [24]
129,077
2008[25]
84,615
12,137 [24]
96,752
2009[26]
82,044
2010[27]
94,310
11,062 [28]
105,372
2011[29]
122,460