Best I can find is via Wiki and that states a production run from the Russelsheim plant of 797,011. But that is all 'Omegas' so presumably including the 'A' - and of course, that's Europe-wide (and N American?) sales - so your estimate of 150k sounds well within the realms of probability. Would love an exact production figure, annoying that isn't easy to find.
So after some digging.... Approximate though it is, the howmanyleft number for all Omegas reads as in its first year of sale (1994) 11k sold. Up to and including 2000 there were 11-15k sold per year. As from 2000-2003 there were a theoretical 7, 6 and 1 thousand sold

.
These figures do not take into account the number lost through what I can only call 'natural wastage' crashes, theft/fire etc.. So the figure of only 1000 sold in their last year will be a little higher, for sure. By that time there were of course 9 year old Omegas out there, some which would have headed for the scrappies at a higher rate than a year or two before.
To move it forward a bit, since production ended, there have been from 2004 - 4k, 8k, 11k, 11k, 11k, 13k, 10k, 9k, 6k, and 5k and 4k in 2014. The numbers of attrition are moving at a steady 1000 cars lost per quarter, interestingly! The graph slowly levels, of course, it's not like in another 4 quarters there will be 'none' - unless you read the Daily Mail-style graphs and think that in Britain there will be an estimated 100million baby-eating Foreigners by 2020, etc...
Looking ten years previous, there are now a reported 560-ish Carltons - a figure that has hovered around that going down
and up for a couple of years now. So in ten years there'll be
something like 500 Omegas, we can infer.
Here's my graph from Howmanyleft...
Year On roads Number increase/decrease
2014 13k -4k
2013 17k -5k
2012 22k -6k
2011 28k -9k
2010 37k -10k
2009 47k -13k
2008 60k -11k
2007 71k -11k
2006 82k -11k
2005 93k -8k
2004 101k -4k
2003 105k 1k
2002 104k 6k
2001 98k 7k
2000 91k 11k
1999 80k 14k
1998 66k 14k
1997 52k 11k
1996 41k 15k
1995 26k 15k
1994 11k 11k Finally I know Howmanyleft isn't accurate, but it's the best we've got!

Possibly interesting, possibly dull to read, but it killed half an hour
