Scott, in an effort to get it Wright, I did a little research for a change and dug up these quotes. Wright doesn't make a big point of whether it means coming or going, but if we take it as coming, he understands the movement to be that "he comes from earth to heaven" (Jesus and the Victory of God, 361).
Here are some other interesting Wright quotes:
First from Who Was Jesus?:
"When Jewish writers spoke of the sun and moon being darkened; when they spoke of angels gathering people from the four winds of heaven; when, in particular, they spoke of a Son of Man who would come on the clouds of heaven - in each of these cases they were using language in this metaphorical way. It is flagrantly absurd to think that Jesus, in saying that sort of thing, envisaged himself of anyone else literally flying around in mid-air on an actual cloud" (55).
"They didn't expect the end of the world; merely the end of the present way the world was run" (56).
And from Jesus and the Victory of God:
"the 'coming of the son of man' does not refer to the 'parousia' in the modern scholarly, and popular, sense of a human figure travelling downwards towards the earth on actual clouds... The word 'coming', so easily misread in English, is in Greek erchomenon, and so could mean either 'coming' or 'going'... The 'coming of the son of man' is thus good first-century metaphorical language for two things: the defeat of the enemies of the true people of god, and the vindication of the true people themselves. Thus, the form that this vindication will take, as envisaged within Mark 13 and its parallels, will be precisely the destruction of Jerusalem and the Temple" (359-60).
These are awefully convenient interpretations for orthodox faith, although not so much for American fundamentalist faith. Wright has a fun footnote: "the interesting spectacle of fundamentalist interpreters taking the metphorical language in Mk. 13:26, 30 ('the coming of the son of man') literally, and literal language ('within a generation') metaphorically," (Jesus, 224 n.96). I agree that some of this apocalyptic language is metaphorical. But I'm not convinced that the arrival of Christ was.