While it's true that this arc is recent, some people would like to get the season sets now as apposed to later. Besides that, they only play Battle Dimension on CN now so some people would also like to see how the saga started again. I have the first two sets and it didn't really bother me that the saga was recent. It was still fun to watch the episode and see how things turned out. Besides that, the main reason I'll be getting the third set in the near future is because of the awesome Tag Battle arc.
I'm sorry, but why would PUSA would release the Japanese version on DVD? I respect and understand that you feel that the Japanese version is funnier has has better BGM, but I don't see any evidence as to why they would do anything with the Japanese version. Most companies who do release the Japanese version are aiming at teenagers and young adults, depending on the show. Considering the material and specific target audience for Pokemon, I don't think too many people would be that interested in it. At least not the target audience PUSA is focusing on for the show.
Besides that, I think that it would be too expense for them to go back and get the Japanese release. I'm sure that PUSA could afford it, but the problem would be if it would be worth doing so considering that they would have to buy the rights to the music, add subtitles, etc. If there was like a massive outcry from the target audience for subtitles, for some odd reason, then PUSA would probably at least give it some consideration. Since I don't think that is the case, I think PUSA is going to stick with going the regular DVD route with their dub.
Yes it was. The third Diamond and Pearl boxset was released during the middle of March. The 17th to be exact I believe.
As for the original question of this thread, the Diamond and Pearl box sets do have different covers. The first one has Ash with Aipom, Turtwig and Pikachu. The second set has Dawn with Piplup, Buneary and Pachirsu on it. The final set has Team Rocket on it. I was surprised with that since I thought that they would put Brock on the cover.