What is the purpose of the rhetorical device in the underlined text?

Ross. Will you to Scone?
Macduff. No, cousin, I’ll to Fife.
Ross. Well, I will thither.
Macduff. Well, may you see things well done there: adieu!
Underlined: Lest our old robes sit easier than our new!

The asyndeton connects ideas related to Duncan’s death.
The irony reveals Macduff’s true feelings about Macbeth.
The metonymy shows Macduff’s concern for their circumstances.
The rhetorical question makes the point that the crown is in contention.