The clerks in my Cingular store make a distinction, for rate plan purposes, between "regular? phones and "PDAs". A PDA, in their lexicon, is any phone with a qwerty keyboard. The best unlimited data plan for these is $40/mo. Regular phones, like the N75, qualify for $20/mo unlimited data.
Except to add logos and shopping links, I don't know what Cingular can do to hobble the N75. It was touted from the beginning by Nokia as a super-duper music phone. Conceivably Cingular will disable 3G, to restrict data use, but that seems unlikely since the unit appears to have been designed specifically for Cingular.
The delay may have something to do with branding related to the merger with AT&T. There may also be some difficulty involving FP1, which I hope (without much reason to hope) will be present.
I don't see any options to the N75 on the horizon. A pocket-sized S60 phone with UMTS 850/1900 is a rare bird.