Yaad aa rahaa hai, meraa gaan!This is news. Bappi Lahiri has recorded the title track for Mani Ratnam's next film Guru, and so marks a new name in the list of singers to sing for A.R.Rahman. News via the A.R.Rahman fans egroup with the source post here (given that Mumbai Mirror has a pathetic habit of not maintaining permalinks).
So Himesh Reshammiya may not actually be that far away from realising his dream of singing for ARR :-).
Trivia question: how many film music directors (apart from ARR ;-) ) have sung for Rahman? I can count only two excluding Bappida: Shankar Mahadevan and M.S.Vishwanathan. I'm sure there are others.