England secured top spot in Pool A with a 14-7 win over Fiji with Tom Mitchell and Dan Norton getting the tries after having defeated Japan and France earlier in the day.
They will now face South Africa who could only finish second in Pool D after they were hammered by USA Sevens winners Samoa 38-7.
The Welsh came out on top of a group that contained Argentina, Russia and Kenya with their 17-5 win over the Argentines their key victory.
They will next face Australia who lost 22-10 to New Zealand in the Pool B decider.
England v South Africa
Wales v Australia
Samoa v Fiji
New Zealand v Argentina