I'm using around 20Gb on my 32Gb Nexus 7 (illustrated books, photos, couple of games, music and some video). Imagine I could pare it down to under 16Gb but why should I bother when NAND costs less than $1/Gb retail?
I like to think a new tablet will give 3+ years useful life and can imagine plenty of ways future apps will benefit from greater storage. Given the devices are not expandable, why should I support built in obsolescence aspirations of manufacturers by saving a few quids worth of parts on a £300+ device? I expect (speaking as a developer) we are going to see growth in 1-2Gb apps over next couple of years which will make the 16Gb systems look old fairly quickly.