Who precisely is going to invest in the "capital bridge" required to transition to the pilotless future? The airlines may reap the saving, but will ATC & airports are simply saddled with the costs? Once the transition is complete ATC & airports are going to want a Return On Investment (ROI). Everyone wants to see their ROI, locked in at minimum risk and it is one hell of a capital expense to transition every single one of the multitude of components at every single airport.
The next issue is until every piece of the puzzle is completely solved at every airport, there will have to be a transition where everyones costs are increased costs as a hybrid system will be required, with both remote & manned operations. The flight deck will still be required to give aircraft the flexibility, so no weight saving there, but with the additional cost of certification & duplication for remote ops for the lifetime of the aircraft.
Aircraft without manned capability will become only be able to fly between certain ports until the end of the transition, and this will limit their valuation in the second hand market. This was exactly the case with very large cargo ships. In many cases they were designed for specific port pairs for maximum efficiency, but were too big for any other routes. If that port pair had competition or suffered economic decline, the capital value of the ship was smashed as it had limited economic value on the secondary market. Aviation has had it's own version of this, the A380. Have the airports that invested capital to support the A380 got their required ROI? I am sure many in hindsight would not have made the investment.
Once the transition is announced, almost every piece of equipment that cannot transition to the new system is devalued as it's operating life is reduced, thus it second hand value is reduced. Previous software investment that is incompatible goes to ZERO quickly. Will the savings for the airlines justify the capital write-downs elsewhere in the system?
If you want to see how costly a major structural transition like this occurs, The Box By Marc Levinson. He follows the transition from Break Bulk cargo to containerisation, and getting everyone in the system to agree and pay for the transition. In the case of break bulk there were literally enormous savings available as every piece of cargo had to be transferred and broken up, stowed at the origin and the reverse process at the destination. This was incredibly labour intensive & expensive, with high rates of damage & loss. Yet, the transition was a Herculean task.
So yes, you are correct, it might save the airlines money, but will everyone else in the system get the savings too? It might be possible, however the bean counters elsewhere will want to make sure they get a cut of the savings and a sufficient ROI to make the risk worth while. One thing that is almost certain, the bulk of any savings are unlikely to be passed on the passenger, rather it will be captured by some entity within the system, be it manufacturers, ATC, airlines or airports.
Read Levinson's book to see how difficult a transition is despite the overwhelming economic savings dwarfing those available to airlines as a percentage of controllable costs. There is much more to this than simply removing the cockpit crew cost. Everyone in the system must agree to transition to something new, with high financial risk, therefore requiring a high ROI before the transition can begin. There are huge risks to committing to some programme without certainty of success.
Is it ultimately inevitable? Probably, but technology will have to advance to the point that it is almost a dead certainty to work before the bean counters in every part of the system decide the risks are low enough. The technology is far too immature for that. Large IT project have a high failure rate and the financial risks are still far too high. However, once the technology has reached maturity, the transition will occur quickly, as it ultimately did for shipping and containerisation.