Indeed, a brightness of "1000 times brighter than Venus" is a bast-case scenario. This comet may very well fizzle out before it becomes visible to the naked eye. It may very well be a new comet fresh out of the Oort cloud, composed mainly of volatile compounds that easily dissipate.
However if the comet does indeed reach those optimistic predictions then it'll be visible for more than a month. Plenty of time for photography. Let's hope for the best!