That ending with DJ and some big party would be nice. If the Iron Throne is still standing at the end and it probably will. Didn't Martin said someone will win this whole thing? It is designed for one person, not two. My point is that at the end of course main protagonists can live through their experiences but when it comes to Jon and Daenerys one of them can be killed. You don't need both to manage after the war situation when you got Tyrion around. Maybe too pessimistic?