my last 2 ai flights on a 3 cabin flight were from del-dxb....the first time the f cabin was empty & the second time there was one person, that too in a pilot's uniform (so i very much doubt it was a paid seat)....even the business cabin both times was almost empty....i think there were 4 passengers (including me) both times....
last year i took a couple of flights in f on the lhr-del route....once i was the only passenger & the other time there was one more person....
i really don't think there are too many people who are willing to pay for a f seat on ai....i would very much be in favour of them getting rid of the f cabin & perhaps have a premium economy section....