Still available doesn't necessarily mean still in production. For example, you can still find a new TD 10, but they stopped making those awhile ago, The same probably applies to the TD20. They could have a bunch in a warehouse somewhere, waiting to eventually sell them.
Honestly, I am surprised that Sony makes them at all. The market is pretty small and Sony has been losing lots of money.. I think the market for 3d is near dead, partially because outside of a few movies (like Avatar, Hugo, Promethious) most 3d movies have been stinkers or even worse, were conversions. Call lack of compelling program material a large contributing factor.
Ironically, the best reason for going 3d could be 3d video. Make your own 3d, watch your family grow up in 3d, relive those vacations in 3d.
Blame the people over at marketing.
I predict that 3d consumer cam development will take a little hiatus until the 4k thing blows over. Once joe consumer sees that their regular programing, still in 780p/1080i, doesn't look any better on a 60" 4k set, enthusiasm will die out. Then, after that, we will see glasses-free 3d displays.
That might catch on.