This will happen only happen when approved by the regulator. For that to happen, someone will have to demonstrate that standing passengers can be safely restrained and capable of withstanding certain g loadings in various directions. So who will cough up for that? Mick the Gyp has the cash, but he has decided not to do so. A seat manuafacturer? It might be worth it but I doubt it. So that leaves the aircraft manufacturer. If this was a good idea they would have done it by now. Even for the greediest this might be a step too far.
PM