According to
http://www.tamiya.com/japan/hobbyshow/index.htm the TRF501X will be unveiled at the All Japan Plamodel Radicon Show 2006 (
) held October 19-22 in Tokyo.
According to
http://hobbyone.blog39.fc2.com/ the list price for the 501X is 79,800 yen. For reference the TRF415MSX MR (latest TC) has the same list price and is sold by Japanese shops for approx. 46,000 yen.