1. Do I need to purchase something else to enjoy the discount coupon for v2.0? i.e. can I apply it to v2.0 "if" your charging for that?

The Discount Coupon doesn't have anything to do with the 2.0 Update. As clearly stated, the Discount Coupon applies to ANY FSDT product, last until December 31th 2011, and can be used (only ONCE) by any Zurich customer. That's it.
The 2.0 upgrade IS FREE, because it's only the 1st step. The screenshots that shows the 2.0 Preview are clearly listed inside the 1st Step paragraph, and that's is going to be free. We don't know how the 2nd and 3rd step will be named, maybe 2.5 and 3.0, but ONLY the 3rd one will be payware.
Since, as clearly explained, the Discount Coupon can be used to ANY FSDT product, even those not released yet, but expires at the end of 2011, if we'll be able to release the 3rd payware upgrade by that date, you'll be able to use it as a discount for that, otherwise you'll have to use it on another product...
2. Love the level of detail in the photo comparison - but honestly don't like the look of the "blue-ish" terminal buildings; any way users can choose "color schemes" in v2.0?
First, you should see it live an in movement, because the eye can be easily tricked by a static screenshot. The way those textures are made is not just "blueish", they are using certain color perception theories, which really only work in movement, because they rely on persistence of vision and the ability for the eye to automatically balance colors in opposition...
In any case, I guess we'll might be able to offer an alternate textures set to download. However, wait to see the scenery live before saying you don't like it...
3. Will you cease support for v1.5.2 or earlier after the release of v2.0 for FSX users; since there is NO v2.0 for fs9, thus I ask?
Again, you confused things. There WILL be a 2.0 for FS9, because 2.0 it's just the 1st Step. Then, there will be another step for FS9, and only the 3rd one (they payware) will be FSX only. Of course, support for old versions will end, but that simply means the last supported version for FS9 will be one version less than the FSX one, but it will be supported nonetheless.