Some people are just naturally faster at learning languages than others for whatever reason. i know people who have diligently studied languages for years and can barely handle the basics. then you hear about people who can learn any number of languages with no problems.
I also think that if you are in a situation where you HAVE to learn a language, then you will be able to learn it quickly. a person living in Korea will probably be able to learn Korean faster than someone living in, let's say, Kansas, as long as you actually move outside of the english speaking foreigner circle and actually talk to people who either can't or won't speak english with you.
It depends on a lot of things, too. How similar the language is to your native tongue, how many languages you've already learned, your affinity for language learning. I achieved Japanese fluency in two years, and passed their hardest proficiency test (JLPT1) in only one year. If you ask me, the best thing you can do when learning a language as different from your native tongue as Korean is to study and practice a lot. Memorizing the vocabulary just flat takes time, but grammar, word choice, and syntax can be learned as fast as you study and practice, and those are what are fundamental to fluency. It's why it's so much easier for an American to learn and start speaking Spanish than Japanese - both require new vocabulary, but Japanese (which is like Korean with different words) requires utterly different grammar, word choice, and syntax.
Also, to a certain degree, time is a tool. I think the seven-year rule comes from two ELL studies that showed that it took 6.5 years for college-level non-natives to achieve native-level vocabulary (~20,000 words). I also think that you can only study so much vocabulary a day before your efficacy starts to decrease, at least in my experience. However, there are also hardcore 8-week immersion courses that are designed to improve your competency stupid-fast. And they do it by utterly surrounding students in the language - they study a bunch of different things (so your mind doesn't lock up) and present material in a lot of different contexts (the average student has to see a word or grammar construct 7 times before he's able to use it effectively, the average AP student 2-3).
And if you ask the US government, it's not a question of years. It's a question of weeks. They train their soldiers to functioning fluency (which would if anything only leave out vocabulary) in Korean in 60 weeks, 4-5 class hours and 2-3 class-prep hours a day.
So based on this and my experience, I'd say it ultimately depends on you, but also that time is exponentially valuable. If you are college-level and study for 2-3 hours a day, it may take 7 years. Yet if you study 8-12 hours a day, you can reach amazing levels in a couple months. Or, if you're just army-level with an affinity for language, you can achieve fluency in about a year. But you have to know yourself because not everyone has the mental endurance to devote that much time to studying something. If it's just 8 weeks, and the person does it during a home-stay program, he may have the stress-relief available to study 12 hours a day. But realize that at some point, everyone burns out and becomes less effective at learning. Once you know where your point is, you know how to effectively utilize your time, and you know from where to start working on your mental endurance.
So all of that to say, I don't really know how to answer your question. There's no way to judge "fluency" or how long it will take you to get there, since everyone is different. But keep studying, and keep going, and you will get there. Especially if you can find a situation where you NEED to use Korean, even if it's just finding someone online to chat with that can't or won't speak English with you.
Hope I helped
Expert in Korean Language