First, I don't think it'd be in Samsung best interest right now to do another Nexus device. The S3 is still selling like hotcakes and the Note2 is right around the corner for North American release..just wouldn't be a smart business move in my opinion.
Second, after seeing HTC's new "J Butterfly" (or whatever it's called) all I can say is WOW, Take my money! This looks and sounds amazing, and I knew they could make a device without that hideous 9inch camera bulge on the back!
I'm not a brand loyalist even though 5 (soon to be 6 with the Note2) of my last device's have been Samsung devices, not because I <3 Samsung, but because they were the best options for me at the time.
That said, I'd love to see a Motorola or HTC Nexus, hell, I'd love to see a quality Moto device on AT&T period, anything other than the Atrix "brand" that's forgettable before you get it out of the store.