If by then a few big companies accept bitcoin, I am certain the amount of people that use bitcoin will be doubled or even trippled.
With that a higher value backing up bitcoin will be a fact. 5 digits may be a little big too optimistic but surely somewhere in between 2k or 5k seems realistic if you ask me.
If big companies will accept bitcoin e.g for shoppings then even if demands will increase still the price will not that increase much. It's because of the regular ciculations of coins that will happen if most of the big companies will continue to distribute coins.