(not going to start that argument again!) aaw go on!

(kiddin)
i was never flexible, compared to average of my age ive always been a bit stiff
although im about as flexible since i started tkd training as when i was at peak in childhood flexibility - so yeah it can be regained but it is always better to have parents who get you into MA's (or ballet etc) early enough to take advantage (saving you a LOT of trouble and effort later)
i cant say whether my max flex has been reduced or not by starting late but i will probably never reach the maximum point of flexibility anyway so no worries

very few people will ever reach max that thier body could ever be so it wouldnt worry about it.
and even if it has had a worse effect than im guessing, its spilt milk so not somthing worth worrying about in that respect as well