The first option is the simplier: yes, a new Targaryen will conquer the shattered Seven Kingdoms, with the supporting old/new noble houses. The second one is the more exciting. The Targaryens can't defeat the usurpers, but none of them is able to defeat the others, so we get a few smaller kingdoms, like the North & Riverlands (and possibly the Vale) against the southern-western provinces. Except Dorne, of course. Like the Iron Islands, they will fight their independence. The question is, whics one is more likely? And if plan 'b' happens, who will rule the knigdoms?