I can't see this being a good idea for Testor's. I love their paints, use them almost exclusively, and I don't want to see them take a hit on a bad business decision.
In addition to various reasons listed above, sci-fi models just don't sell as much as the more popular aircraft and armor kits. They'd be trying to sell to a much smaller market.
Additionally, I don't think most sci-fi modellers are sticklers for exacting colors. Its one of the reasons many of us build SF in the first place, because we're free to experiment. Also, a lot of SF kits are bought by kids who are just cutting their modeling teeth. Getting the seams to look right (or getting a spaceship you can play with) is more of a priority to them than exact color matches.
Lastly, I think anybody who really wants to make sure that they get the right Enterprise-D azteking colors has probably already done research on just that aspect of the build.
So really, it would only be a percentage of SF modelers who would buy the paints, reducing the demographic even more. I just can't see that being good business sense.
I would like Testor's to make some better flesh tones, or some weathering colors. If they could make colors similar to Tamiya's Buff, Deck Tan or Earth, that would rock!