I believe that if you praticed what you learn hard enough, you'll be about to speak japanese well. I depends if you be able to speak fluently. You may not be able to speak full japanese though, I'm sure that there will be some topics that won't be covered here.
It's really based on your desire to learn the language in the first place, put your soul into it and given with time you'll have it down second nature like.
Well, if you really like Japanese, like me, I think you would be able... if you would go, after you finish those lessons, to a Japanese class. I think that if you want to speak it well you have to practice it with people. Maybe if you won a schoolarship you would be able to go to a Japanese college. My dream :D