C++ today is not the same as it was some 15-20 years ago.
Likewise, D3D today is not the same as it was in 2002 (D3D9).
I think the analogy here is more like: someone decides to release a textmode application.
Yes, nothing wrong with textmode, we used it all the time, in the good old days. But most people come to expect a GUI these days. So it's not a very logical choice.
The key is you choice what you want, and no one else is forcing you for it. Blizzard can go openGL if they want, which is totally up to them. You, as a customer on the other hand, can choice to buy it or not. The choice is yours.
Rather a technology will survive depends on whether people use to use it, not rather it is new. Dx9 has been around, killing any competitors at the time and still kicking around. Instead of making Dx10 backward compatible, MS decided to unify stuff their way. Again, the decision is theirs, but rather people is going to follow is another story.
I can run a piece of C code written 30 years ago with the most recent C compiler. Blizzard can run their SC/WC engine that was there and run it on Dx9. It is MS stupidity for not allowing forward/backward compatibility for cases like this. WoW's next expansion is on Dx9. Diablo 3 is on Dx9. SC2's expansion will probably in Dx9. So what? You new video card runs Dx9 without issues. Your new OS runs Dx9 without issues. What is your problem?
The game runs great, regardless of the brand of your video card. Nvidia took a step forward in fixing AA problem on Dx9 that was there many years. ATI also did that too, just not on SC2. Maybe they will do it, and I believe they will at all cost, but until then, no AA. Is that a big deal? Well unless you are using 32" display and stick your face on the display, it really isn't a big deal.
Of course you or others can make a mountain out of moles, but since Richard Huddy insisted that Nvidia played dirty and their ATI video cards can do AA just as well as Nvidia and the only reason that they can't do it in Batman was because Nvidia blocked them. Maybe they NEED to prove this on SC2 this time. Interestingly, the offical response from ATI on SC2 was not done by Richard and stated that their engineer decided NOT to implement it. I guess, in terms of forum rage wars, Nvidia fanboys score one. Nvidia video cards can do it, ATI video cards can not.
Again, practically speaking, it is just a mole. Nothing big.