The safest investment is to purchase some BTC and then keep them in cold storage until you want to sell your profits.
No... the safest investment is the pre-purchasing of anything which you can store securely
for long enough that will definitely help you meet a guaranteed future need.
Such as water, food, shelter, medicine, ....
These items don't lose value, because you will definitely consume them (not sell them).
Purchasing and socking away BTC is comparable to stuffing US dollars in a safety deposit box.
which, by the way, is essentially guaranteed to lose money, at whatever the rate of inflation.
It's not fair to say BTC is safest possible investment, since it's not even that "safe" in volatility
terms, there is a significantly high chance BTC could lose 99% of its value in a short time;
(it's value could then go up 1000x, a few years later after most investors sold it at the bottom).
Dollars have a longer history and larger number of users, and therefore these stable currencies
are much less likely to experience comparable levels of volatility in the foreseeable future.
No investment is really safe, though, they all just have a different risk profile.
To optimize risk/reward, most people will want to have numerous investments of various sizes,
and avoid having direct correlation between assets meant to be diverse.
It does no good to have equity in 100 companies that will all fail, if there is a shortage of type Xyz widgets.
