what would be the official date of Magento 1 sunset?
Superseding the superseding edit: June 2020 is the official EOL as of 2018.
Superseding edit: As was recently announced on Twitter by my CEO at Magento, this answer to this question is currently (6 June 2017) pending further announcements.*
Magento 1.x end of life is November 2018.
Edit: Tweet from our Head of Product: "November 18th 2018 to be exact."
According to this post we can officially say bye bye to Magento 1.x in June 2020 straight after T-20 cricket world-cup.
https://magento.com/blog/magento-news/supporting-magento-1-through-june-2020
Magento 1 is a great piece of software, the best shopping cart I ever used starting my experience long time ago with osCommerce. Those who consider it old they did not evaluate the treasure consisting of articles, true solutions, tons of free and paid extensions, themes, tutorials, books and many more. In any moment I can find something related to my issues for Magento 1.
What Magento 2 is actually offering? I hear a lot of people wanting to upgrade but did they evaluate the opportunities? A completely different platform adapted to "our days", a few expensive extensions, lack of support, a longer period of accommodating, missing books and tutorials. The only great thing I appreciate is the bug reporting system in Git. It will take around 3 - 4 years to get a complete competitive and powerful switch catching what Magento 1 offers right now.
Today Magento 1 is like a person around age of 40, mature. Everything you want from it there is on the market. Abandoning Magento 1 is a bad idea even for security patches, but if you look deeper they abandoned it long time ago about 2 years ago. Just see how slow the team reacts to bugs reported in their system. Only the community keeps it alive because it's still the best shopping cart on the market.