I should reverse a bit. I've seen some say August/Sept and others say April/May. If it is April/May it will harm the club game. As @Leinster Fan says it clashes with Premier league but instead of clashing with start it will go against ending. And it will hurt the club game because if you try over compensate the club game then it is a case of piling a whole domestic and European season in to late Sept to March. Using Leinster who are best example at moment. When is the window to aim to peak for and to relax it on. Also if a Lions tour etc is still in the cards how does player welfare kick in here. Also a RWC. The only way this will work and I suspect is being viewed is global world leagues and club leagues being Hemisphere based. It is the only way. So no Pro14, Premiership or Top14. No European Cup. More a European League with Div 1, 2 and 3 etc.