Demand probably will grow, but there are only oh so many people that can splash $1600 on a 45, so if more copies turns up (and they seem to do) the price will come down.
It's always a good thing when major label 45s that are considered rare turns up on eBay and goes for a stack load of money because more often than not, the high end result smokes out more copies (perhaps due to some owners just not being able to hold on to a 45 if the going rate is THAT high, but also because 45s that people outside the soul collecting scene might never have considered to list now starts to appear).
It'll be interesting to see what the two current copies on eBay will end at.