Paddy Jackson will leave Perpignan after a single campaign in France, joining London Irish for their return to the Premiership.
Former South Africa head coach Heyneke Meyer will remain with Stade Francais for at least another two years.
It promises to be an enthralling climax to the battle for Top 14 play-off spots after Stade Francais claimed a derby win over Racing 92.
Grenoble look to be heading for a relegation play-off after losing at home to their nearest rivals Agen.
Toulon centre Mathieu Bastareaud explained why he is headed for New York after the Rugby World Cup.
Greig Laidlaw's boot and a pair of tries from Apisai Naqalevu helped Clermont Auvergne battle back to beat Stade Francais on the road.
Top 14 leaders Toulouse enjoyed a fine day as several rivals were beaten amid a series of dramatic finishes.
Franck Azema will become the longest-serving coach in Clermont Auvergne's history if he sees out a new deal until 2023.
England international Ben Te'o is one of eight players who will be leaving Sixways at the end of the Premiership season.
Sunday's semi-final against Leinster will see Toulouse players wearing a special kit that includes an image of Notre Dame.