Thinking about Mike, it's obvious that after Walter killed Gus that Mike should be next. But the fact that the writers used Mike to make many people come to hate Walt............ essentially making Walt's character come full circle makes me believe that the show will end with Walt as the new Ice Kingpin.
Mike was the last training point, for Walt to fully see, understand and accept that there are no half measures in the drug game. Instead of killing Mike, and taking the long arduous road to building up his drug business, Walt again tried to take another half measure.
I would say all his dealing with these different levels of drug kingpins, were stepping stones to show how Walter White became the finished product known as Heisenburg. Taking us, the viewers along the ride showing his stumblings, his half measures, his growth, his transformation, his alchemy.
The last step of this process is for him to do now what all drug kingpins have to do, which is fight for his turf against encroaching enemies
I think the final eight episodes are going to circle around a war with the cartel Mike was working out that 15Mil deal with.
Breaking Bad to me is one of those shows, where they show you the final episode and everything is flashbacks working its way up to that point. Which leads me to think that the entire show is working from that storyboard, with is Walter White unassuming middle aged, middle class white male as the drug kingpin... I would say think Sandman in Training Day.
The ending now depends on what type of message the show creators want to take ... Do they want to take the cheap, audience pleasing route of killing Walt off in the end, or end it as him being the ultimate villain, the new Ice kingpin ..... or that whole teaching route of crime never pays with him ending up in jail and everyone hating him
I'll add more to this later on