Similar situation
I have two approved I-140's and two pending I-485's (NIW and EB1EA). Recently, we got our I-485 approved under NIW . I talked to my attorney whether I have to withdraw pending i-140 and 485 application. The aswer was "NO" you don't have to withdraw, USCIS will take care of those pending application.
See below for details:
I-140 NIW/I-485 (NSC) : RD Sep, 2005
I-140 AD: Jan, 2006
I-485 AD: July, 2007 (received cards for myself and spouse)
I-140 EB1EA (TSC):
RD: May, 2006; AD: July, 2006
I-485: RD Sept, 2006, pending