I feel that blockchain is here to stay but can't help thinking there might be a SLIGHT possibility that BTC wont get mainstream. In the UK, I don't know of one place that accepts BTC on the high street and I'm not a hermit.
I was filling the car up a few days ago and thought what it would be like to pay with BTC.
Maybe it will never be illegal in the UK or my government would have said so already but it may never become mainstream and ONLY niche.
The price we dream of for a BTC to be 5 figures is the day my mum has her own BTC account which she takes travelling and she 55 years old. Blockchain is staying but can it force its way into mainstream if given time. Will it happen or NOT. Is the fact that japan have adopted it and they are a developed country means that its ONLY a matter of time the west adopts it.
10-15 years is hard to imagine and so far down the road...
It depends on what you define as mainstream. If you think it is going to replace a majority of the economic system then you're probably long as it stands right now; there's simply nothing to really determine whether or not there is going to be a replacement of that scale, meaning that it is unlikely in the first place. Plus the governments won't rescind their power.
Now if you are wondering about when it becomes something a lot of people use in conjunction with their current financial situation, then it really doesn't have a general time when we could see the switch for the common man. It'll likely happen over the course of a week or two, if it happens, in a sort of viral "everyone is doing it" way. That's the most likely way we could see a change. Otherwise, a very long, drawn out and potentially full-of-legal issues problems.