Unfortunately FCP 5.1 is an upgrade, not an update.
BJ
Release history
Date Releases
NAB 1999 Final Cut Pro
MWSF 2001 DVD Studio Pro
March 2001 Final Cut Pro 2 [1]
December 2001 Final Cut Pro 3 [2]
April 2002 Cinema Tools [3]
NAB 2002 DVD Studio Pro 1.5 [4]
NAB 2003 Final Cut Pro 4 [5], DVD Studio Pro 2 [6], LiveType, Soundtrack, Compressor
NAB 2004 Final Cut Pro HD [7], DVD Studio Pro 3 [8], Motion [9], LiveType 1.2, Soundtrack 1.2, Compressor 1.2
August 2004 Production Suite [10]
NAB 2005 Final Cut Studio [11]: Final Cut Pro 5, DVD Studio Pro 4, Motion 2, LiveType 2, Soundtrack Pro [12], Compressor 2
March 2006 Final Cut Studio 5.1 released as a Universal application [13].
NAB 2007 Final Cut Studio 2 [14]: Final Cut Pro 6, DVD Studio Pro 4, Motion 3, LiveType 2, Soundtrack Pro 2, Color, Compressor 3