Yes but people were also not clamoring for the iPod either when it was introduced. Apple is very good at showing people what they want, even when the market is not already defined.Short answer: 0 < P < 1
Longer answer: I wouldn't bet on it. Has the lack of waterproofing had a significant effect in iPhone sales? Have the Sony's taken the market by storm with people lining up to get them? Or the Samsung S4 Active; were those in high demand? Are there threads here showing people are clamoring to sell their iphones and go buy an S5 because of the water resistance? No? Then probably not a feature Apple will feel compelled to worry about.