most probably i would like to use it every day for such simple things as buying food or going to the doctor, i want bitcoin to be mainstream
Exactly, thinking about next 20 years would be a weird, its better we concentrate in present and keep on spending our bitcoins on daily basis, either digitally or physically.
Thinking about the next 20 years is extremely important. Not only regarding what happens to bitcoin, but also regarding your financial well being in the future. You may have a stable job and income now, but what if you lose it? Are you building enough to retire comfortably? The list goes on. It is therefore very important to not only focus on the present, but also on the future!