Mk6 was an exception, usually each generation of Golf involves a new chassis. So I'd expect the Mk8 will be the debut for an MQB Evo platform. Mk7 will probably have a longer life span than the Mk5 and Mk6 did individually, but not as long combined, if that makes sense!
Audi usually do facelifts so the A3 8V will probably get an interim update to keep it fresh