Canon 24-70 f4 IS ???????????

I know why they did not come out with the 24-70mm f2.8 IS....... because it would kill sales on the new 24-70mm f2.8 II.   But WHY did they come out with the II instead of an IS version???  How about a II with IS.   I am intrigued with the new 24-70mm f4 IS BUT.....   I am conserned that I would want the 2.8 every now and then.   Anybody know why did not go IS with the 2.8  II??

I know its possible... I have the Tamron VC version.

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Bob Keenan
http://www.bobkeenanphoto.com