Well, according to my definition of folksongs(which of course is only mine not anyone else's), the answer to your questions are(1) none of them are folk songs. (2) none of them ever will be: because we know who wrote them all, and they have not been subjected to the oral tradition.
However, it is feasible that the information about their origin may be lost due a breakdown in civilisation, and they will start to modify themselves organically. In which case I would put money on "Summertime" and "Que sera,sera" turning into folksongs quicker than most.