Licenses for AX 2012 R3; difference in functionality between AX 2012 and AX 7

I want to go with Microsoft Dynamics Ax 2012 r3 for my organization.

I came to know that Microsoft is launching Dynamics 365 and stopping licences  for Dynamics Ax 2012r3 from June 2017.

that means i cannot get licences after june 2017.

If i get the Licences and implemented in my organization How many years i can use the software without any fuss as they will updates and support after 5 years. Then i Forced to move to Dynamics 365 and again i have to pay the implementation charges.

I also want to know the difference of Functionalities of Dynamics Ax 2012 r3 and Dynamics 365.