Many things changed in new Dynamics AX. Following are few of highlights for architecture perspective...
~ Web based client (HTML5/JS) - application accessed from many clients
~ No remote procedure call (RPC)-based communication with the server
~ Application hosted in IIS
~ Cloud based
~ Lifecycle Services - easier to deploy, test and maintain environment

Dynamics AX Server Architecture
~ Visual studio as development environment~ New design patterns for forms
~ Customization with extensions & overlayering
~ OData service - enables access to AX data from different clients
Microsoft Dynamics AX Application Stack
Application stack split into different models..~ Application platform - runtime data access, client, ..
~ Application foundation - GAB, Source document, Number sequence,..
~ Application suite - Finance management, Inventory, .....

Power BI Integration
~ Power BI - allow to connect multiple data sources to create reports and dashboards