Can a single engine on an A320 provide wing anti ice for both wings in the air ?
It would probably be a single point of failure if one engine wouldn't be enough to deice both wings.
For this reason there is a cross bleed selector so that the remaining engine can feed the wing on the opposing side.
Here is a link to a computer based training video of the A320 explaining that a single engine bleed is enough for both wings but not for both air conditioning packs and wing anti ice at the same time. So to use have wing anti ice with a single engine you need to turn off one pack and enable cross bleed.