I don't think Intel is too worried...drivers and software still have a long way to go for 64-bit computing. However, Intel doesn't want to be caught off-guard or behind the times when the software and drivers do arrive, which might be why they are releasing their 64-bit chip soon.
Also, Intel's x86 64-bit process is supposedly not compatible with AMD's x86-64 (or x87). This means that two different Windows will have to be written, as well as two different __________s (name your software)...Intel wants to get their foot in the door and get recognized. As I said above, they don't want to be caught off-guard or the behind the times when the technology becomes more complete.
Or, they may have been developing it for some time now, found a breakthrough in one form or another and have the release date pushed way ahead of schedule...i.e., soon. Either way, it seems Intel will not let AMD just walk away with the crown for 64-bit computing (when it becomes a reality for consumers).
But, IMO, it's just good ol' competition and intimidation. Intel said nothing of 64-bit for the longest time, then when AMD start building some steam, they announce that their own 64-bit is coming soon.
Damn Rambus.