I would guess $10k for late 2018 or early 2019, but honestly with the way this year is going (more than tripling in just over 7 months) I wouldn't be totally shocked to see a couple more big bull runs in the next 6 months (we might be starting one right now!) and hit $10k by early 2018.
You are an optimist. I would not be so sure that the price rises so much. I believe in bitcoin, but I see no reason for such growth. Maybe it will reach $ 10,000, but it will not be as soon as we want
Sure I'm an optimist, why would I be a pessimist?
But I'm not overly optimistic, otherwise I'd be thinking it can hit $6k this year (which it might) and then double every year after that which would have us at $96k in 2021 - which I think is within the realm of possibility but I don't think there is any way it will be that high that soon, I think $30-40k by end of 2021 is much more realistic. But I would not at all be surprised if my own personal goals for bitcoin ($10k in 2018, $50k in 2022) end up looking pessimistic in hindsight during those years.
Your pessimism seems to be geared around not seeing any reason for it to triple from the current price earlier than 3 years from now. It just more than tripled in 7 months. It just went up almost $500 the past 3 days. 7 months ago I bet you would have said it'll take 3 years to hit 3k as well! The reason is the same reason why it could more than triple in the past 7 months, because bitcoin userbase is very small but is growing exponentially. Furthermore rich investors are just barely starting to get into bitcoin. $10k ain't gonna come in the next few months, but it ain't gonna take THAT long. Bitcoin can gain $400-500 over a weekend, or a couple thousand over a month or two, as we've seen this year. It's not gonna take 3-5 years to gain only another ~$6600. Maybe three more bull runs (this Fall?, next Spring?, next Fall?) could put btc at $10k.