What will happen to Bitcoins, or more specific, to the price of a Bitcoin, once all 21 million are created?
... absolutely nothing will happen, since by that time the block subsidy will have already been an insignificant fraction of mining rewards ...(1) Assuming Bitcoins are widely used by then, there will be lots of trades - and lots of transaction fees.
... or ...
(2) Assuming no one will use Bitcoins, there will be no transaction fees.
I'll bet on option 2
There are already many places where you can spend your bitcoins, and the number of places that accept bitcoins is likely to continue increasing in the future as Bitcoin becomes more widely known.
Just because there are places where Bitcoins could be spent does not mean people do use them.
The places you mentioned are more or less exotic (e.g. a book store for "Document preparing the common competition in french politics sciences" hrmmmm ...). Once I can bay a toaster on Amazon using Bitcoins I will be convinced. And happy
