What many players who don't like the sets seem to miss on is that this is something entirely new in the game. Blizzard has always done recolored versions of armor, but this is the first time by my reckoning that they have done evolutionary tier gear. [EDIT: This isn't entirely true. Reader Suzaku pointed out that the leather armor from Level 60 PvP sets evolved. My bad on missing out on that.] When I first encountered Blizzard's new multi-tiered PvP gear system, I was apprehensive about the next season's gear because I was afraid it would be difficult to match pieces visually. Arena gear had, prior to Season 5, been mere recolors of PvE raid sets, so there was no contuity from the one season to the next.
The problem with that was upgrading from one season's set to the other created visual clashes. As much as we like to min/max, PvPers like to look good, too. Enter Season 5 and the multi-tier gear system. There were three different sets of gear but all of them melded seamlessly into the other, with minor discrepancies in color. The introduction of an entirely new set of gear with completely different designs in Season 6 would have invalidated not just one but three sets of gear. However, the new design philosophy builds upon the older models, evolving -- as Alex put it -- like Azerothian Pokemon.
If you don't like the base sets (Season 5), then obviously, fancier shoulders and helmets won't do anything for you. It took me a while to digest the understated designs of Wrath PvP gear, but the whole nipples-of-dragons argument made sense to me. Don't get me wrong, I still pine for faction-specific PvP sets, and I think the old Marshal / Warlord item sets were still some of the best designed gear, but I have grown to appreciate this new design philosophy. When I'm raiding, I'm in shiny green and gold, fancy winged Gundam armor. But when I PvP, I slap on a gunmetal set that's designed for business. I like that. I think it's a great idea.
The potential is pretty awesome. Remember that Blizzard's artists can just as easily change the skin of other pieces, not just "grow" the shoulders in future sets (if I'm not mistaken, they've very subtly changed the Shaman chest graphic). It's extremely possible to have different, badass PvP sets in future seasons, but hearkens to the base designs of Season 5. Zarhym stated that the looks of the sets would improve over the seasons -- while the original designs might have been underwhelming for some of the classes, the new sets are an improvement.
Instead of expecting to see a new set each season, I'm excited to see how it evolves from the old. How the design team will utilize existing themes and build upon them. For the first time ever, we'll have entire sets that are direct upgrades or evolutions visually from their lower tier counterparts. As an artist, that's a different design challenge altogether. As underwhelmed as I was with the designs of the first iteration of Wrath PvP gear, I'm pretty stoked to see how far Blizzard's team will take this.