Support for Exchange 2007 ends after 10 years on April 11, 2017, so from April there will be no more technical support, bug and security fixes or time zone updates for Exchange 2007.
So if you are still running Exchange 2007, you should migrate as soon as possible. Exchange 2007 cannot be migrated directly to Exchange 2016. Direct migration is only possible to Exchange 2010 and Exchange 2013.
A migration from Exchange 2007 to Exchange 2010 is no longer recommended, Exchange 2010 support ends in January 2020, while Exchange 2013 is still supported until April 2023.
Even if it probably doesn't affect many people anymore, here is another document with the options:
Exchange 2007 End of Life Roadmap
When I think back to the problems I had with Exchange 2007, I'm not so sad about the end of support. However, I would consider the introduction of the Exchange Management Shell, which many people had problems with at first, to be the best innovation at the time. However, I don't count the seemingly 10,000 deployment variants as one of the greatest innovations.
RIP Exchange 2007!