It seems that several decades has passed. We also don't know the effect of Psy powers on longevity of human life, for instance- more powerful Psys may, potentially, live longer. From what CraigStern mentioned earlier, it will be someone we've met before, but that doesn't mean it will be someone very prominent.
The fact that he is the Nameless One may support the genderless Hero with no name, but then he is defined as a he in TSoG (the old coger) and lack of name may, as said above, be simply to add suspense. It seems like we'll find out at the end of TSoG (would be logical). The part about parents may be indicative of it being David, since the Main wasn't around when Unlce Falstaff and, presumably, the father of the Main passed away, whilst David migh've been. (The father is mentioned in TRPG1 and in TRPG2 David says that there is no one left, but them- David and the Main.)