I'm not aware of any ADC monitors that had firewire - I'm pretty sure it only carried power, USB (1.1 only, not USB 2.0), and a DVI signal. I might be wrong about this, though - anybody know of ADC devices with firewire?
At any rate, DisplayPort - even Mini DisplayPort - is the new DVI, and it's here to stay. Now, if the use of VGA long past its obsolescence is anything to go by, people will still be using DVI commonly until we're on the next port up from DisplayPort. That said, improvements from DVI to DisplayPort are much more marginal than the step up from VGA.
Still, you can never be sure. After all, 3D is the next big thing these days, apparently. Who knows?