Isaiah uses the "prophetic present" to show the destruction of Palestine. They are not yet "dissolved" as Isaiah speaks, in fact, they might be rejoicing from their temporary salvation from the Assyrians. Nevertheless, the world of the Lord is against them, and it will come to pass, therefore Isaiah "dissolves" them in the present tense.
The smoke from the north is an image of destruction. As has been noted, fire is a part of ancient warfare, and this smoke is indicative of such a destruction.
Literary: The term "north" is interesting in that it might be a symbolic direction as much as a cardinal one. Note these uses of "North" in Jeremiah:
Jer. 25:9
9 Behold, I will send and take all the families of the north, saith the LORD, and Nebuchadrezzar the king of Babylon, my servant, and will bring them against this land, and against the inhabitants thereof, and against all these nations round about, and will utterly destroy them, and make them an astonishment, and an hissing, and perpetual desolations.
10 Moreover I will take from them the voice of mirth, and the voice of gladness, the voice of the bridegroom, and the voice of the bride, the sound of the millstones, and the light of the candle.
11 And this whole land shall be a desolation, and an astonishment; and these nations shall serve the king of Babylon seventy years.
In these verses, Jeremiah associates Babylon with "all the families of the north." These "families of the north" including the King of Babylon, will come to afflict Israel. Babylon is somewhat North of Judah, but perhaps better Northeast. Compare now to another passage in Jeremiah:
Jer. 47:1
1 The word of the LORD that came to Jeremiah the prophet against the Philistines, before that Pharaoh smote Gaza.
2 Thus saith the LORD; Behold, waters rise up out of the north, and shall be an overflowing flood, and shall overflow the land, and all that is therein; the city, and them that dwell therein: then the men shall cry, and all the inhabitants of the land shall howl.
3 At the noise of the stamping of the hoofs of his strong horses, at the rushing of his chariots, and at the rumbling of his wheels, the fathers shall not look back to their children for feebleness of hands;
4 Because of the day that cometh to spoil all the Philistines, and to cut off from Tyrus and Zidon every helper that remaineth: for the LORD will spoil the Philistines, the remnant of the country of Caphtor.
Once again, we have trouble arising from the "north." In this case, verse 2 has "waters rise up out of the north." Most interesting, however, is that this is a case where the text also contains the information on the way the text was fulfilled, for verse 1 notes that this was a prophecy that came "before that Pharaoh smote Gaza." Yet Egypt is south of Palestine.
North may be simply a symbolic direction from which bad things come (see Isa. 41:25; Jer. 4:6; Jer. 6:22; Jer. 13:20; Jer. 50:41; Jer. 51:48.)
2 Ne. 24:32
32 What shall then answer the messengers of the nations? That the Lord hath founded Zion, and the poor of his people shall trust in it.
The message the world will understand when these things come to pass will be that the Lord is watching out for his people. This triumphal Lord will bring peace and safety to his people (in itself a reversal from their historical trials.) The implication of the Lord is that these nations who send messengers seeking succor may also enter into his protective rest, if they too become part of Zion.