baggins
If William dies then its difficult to see it being a decisive Norman victory. Most likely both sides fall to squabbling overthe succession to their respective states. However the English are at home with additional support available. The Normans [along with Bretons, French and Flemish will be disputing over power in Normandy and related regions so the bulk of the force will be mainly concerned with getting home.
As such a period of disorder in both regions but the key change is that Saxon England would survive rather than being drawn into the French sphere. Might get latter clashes but unlikely the Normans will seriously threaten England again. Or as a result Ireland, Wales or Scotland. Hence probably less interaction with the continent in the near future. [Although if Normany or related areas continue to be very powerful and militarily aggressive the 'Auld Alliance' might be between England and the French monarchy, seeking to keep a common threat in check.
Steve