Probably not. The deals on the Speed 6 means it's failing in the marketplace, hence a higher fall off in depreciation. Time will tell, but the Speed 3 by far is a more popular car, the the Speed 3 is way more of an enthusiast car then the Speed 6. A lot of Speed 6 owners didn't buy it even thinking of it as an enthusiast car. They figured, they could get a 6 speed manual, powerful AWD upgraded version of a regular 6, and essentially, that's exactly what they got. There's a much larger difference in HP between the top of line regular Mazda 3 then there is the top of the line regular mazda 6 compared to the Speed models as well.
The values will end up closer to even, even though the Speed 6 cost more money to make. Mazda is making money off the Speed 3, but probably breaking even or even possibly losing some money on the Speed 6.