Joseph I has a male heir: how does it affect the War of Spanish Succession?

If the Emperor Joseph I had a surviving male heir (IOTL his only son died in infancy) how would it affect the War of the Spanish Succession? Now there would be no risk of his brother Charles becoming both Emperor and King of Spain and upseting the ballance of power. Would the anti-French alliance continue the fight or the Bourbons would still get the Spanish throne?
 
I don't see why not. Unification of the Hereditary Habsburg Lands was the major concern of the Dutch and English and was why they back out after Joseph's death. If his son Leopold survives, I don't see why they wouldn't push for total victory, after all Charles had already been crowned at Madrid as Charles III of Spain.
 
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