Consider: "It may rain tomorrow."
Is this about permission? Surely not, unless the speaker is God. This sense of the word 'may' refers to possibility rather than permission.
Without further context, the sentence above is best interpreted as being similar to this sense, although technically your choice of "can" is not ungrammatical.
However, you could argue that your choice is equally valid given sufficient context. Take for example, a pair of pranksters discussing possible pranks:
"Somebody can drop a banana on the ground...."
In this case 'can' gives a stronger sense of potential than 'may', appropriate for suggesting a possible course of action.
Note how when I suggested that you "could argue" that your choice is equally valid that I used the past tense? That shows a higher degree of doubtfulness.