Why Dust attacking is an issue to IOTA is because the tangle has only one ledger. With sharding, the tangle can have ledger for every shardings.
If the tangle has one million shardings, dust attacking won’t be an issue anymore.
What we can do is giving a size limitation for a ledger of sharding,
if a ledger is larger then a setting parameter, a sharding will spit into at least two automatically.
When dust attacking attacks on a sharding, the ledger would expend and finally spit into two. Because size of a ledger is limited dust attacking won’t damage the tangle
That could be a dust protection solution.
And b4 Coordicide, dust burning solution still can be used.