I'm currently looking at a few as I can upgrade from April. My possibles are the Xperia S, the HTC One X, the Samsung Galaxy S3, and the Samsung Note.
Saw the Note in the flesh yesterday and liked it a lot, but it does seem a bit too big if I'm honest, so that is probably my fourth choice.
I like the HTC One X as I do like my Desire, and I confess I've no plans to root or flash my next phone (rooted my Desire, tried a custom ROM, didn't like it, went back to Sense) so the fixed battery doesn't really bother me, and I've no intention of putting music or videos on my phone so the storage space is fine. It does look a bit "meh" though, design-wise, and I want to read some reviews of it.
As for the Sony, the two best phones I've ever had were Sony Ericsson handsets (a K800 and a C905) so that one is calling out to me, and as well as looking quite smart I've read a couple of great reviews of it. The fact that it is dual core doesn't really bother me as I use my phone for calls, texts, and bits of e.g. browsing and Twitter, so I won't be using it for games or media.
Finally, the Galaxy S3 is the one I'm really looking forward to seeing, so hopefully we'll get a glimpse of that one before long.
Ultimately it will boil down to two key things for me: do I like the look of it when I see it for real, and how much will it cost to upgrade.