That's also one reason why many people think Quattro has "better colors". It's mostly because its auto white balance is superior.
And they could manage to make the Merrill processing for Mac users slower with SPP 6.x compared to SPP 5.5.3. Is this the plan, to make the dp/sd Merrills look worse?
In my opinion it is an extremely unprofessional and consumer unfriendly attitude from Sigma to drop support for these cameras.
Not too long ago, the sd1 was an extremely expensive flagship and "medium format" competitor. Now it's a dead horse. (at least for the Sigma company)