There is apparently an ongoing registration campain on the JP SONY website (until the 31th of march 2016):
https://www.sony.jp/digital-paper/support/touroku/
In the FAQ we can read (google translation):
"Q13: when you register, what are the benefits?
A13: If the registration I was just up to March 31, 2016, it will be considered as the warranty period from the date of purchase for three years.
Also, we'll give the guidance of future updates and events."
Considering this, it seems that SONY still has plans to keep updating this product.
This is good news IMO!