It also depends on what country you are living in when you are studying.
I have studied for a little over two years, and 80% of that time has been in Japan. I have been teaching English at a high school, so I haven't had any real lessons in Japanese, and my role is 'English speaker' but I have lots of free time to study at school. I have a girlfriend who is not Japanese, and most of my friends here are foreigners.
I can read a book or magazine article on most most topics without a dictionary, although of course there will be words and sentences I don't know. But its not difficult or stressful anymore. The speed...maybe about 1/4 of my English reading speed, if I have to use a dictionary, obviously slower but I understand more.
I am past the point where, by rephrasing and changing what I want to say, I can express almost anything when speaking, so that's good. But my ability to hold a conversation is affected by many variables, such as topic and who I am talking to. I am sure I make lots of mistakes and say unnatural things, but that's what learning a language is like.
Can understand and enjoy watching TV/radio programs etc. Struggle with variety programs that use lots of slang, or newsprograms because they use dense and unfamiliar words. However, as long as the program has subtitles in japanese, I am ok (reading is better than listening by a lot at this poitn).
Writing--with a pen, I am losing that ability very quickly. And it doesn't bother me at all, since typing kanji on the computer is easy as pie.
Anyway, if you really dedicate yourself, even if you come to japan to work as an English teacher and had not studied the language before, I would say after two years you could reach this level. All my reading has been Japanese since I came and I only watch Japanese TV (not internet at home and can't use utube at school), so those skills have improved the most. If you are more sociable, make japanese friends, or make a japanese girlfriend/boyfriend who you only talk to in Japanese, obviously your speaking and listening skills will be better than this.