bloodline (a good netflix show, i recommend) has a pretty self-contained first season, to the point where everyone was kinda surprised there is actually going to be a second season. then it was revealed that the writers pitched 5-6 seasons initially, so i'm guessing that that is pretty standard. however, in this instance, i agree with dom that they probably knew the general trajectory and that it would end with 'walt will die, and before he does there will be an inevitable showdown with his brother in law'.
there's some info here that kinda answers your question - basically they didn't start thinking in great detail about how to end the series until S3:
http://www.ew.com/article/2014/04/14...tter-call-saul