It's kind of the same for me.
I was really super excited when Johto League Journeys was just starting. So much so, in fact, that I was jittery and wiggly watching the first couple episodes. And I was also extremely excited with the beginning of the Hoenn saga, especially when they aired the first two/three episodes ahead of time on Kids' WB. Oh, that was great! ^_^
But I wasn't as
excited for the start of DP, and I'm really not all that much excited for the start of BW. I haven't warmed up yet to many of the Pokemon designs, and I certainly haven't warmed up to any of the human characters we've glimpsed yet - especially this awkward Iris girl - so I guess my mood isn't right. (It probably also doesn't help that being staff on this forum makes it next to impossible to avoid spoilers, so DP wasn't and BW won't be exactly 'new' to me like Johto and Hoenn were...)
At the moment, what I'm most excited about is seeing the Sinnoh League. With another 6-on-6 versus Paul, the Johto team's triumphant return, and a battle with a Darkrai, the League is shaping up to be a great television experience for Pokemon fans.
Oh, and I'm going to miss Brock a lot. I'll miss Piplup, too. Glad to be rid of Dawn and her other Pokemon, but Brock and Piplup are A-OK in my book.