The spiderman moves make money for Sony/Columbia. The first one cost about 150 million to make and all the sequels cost between 200 to 300 million. Every single of the four spiderman movies made over 750 million, and thus these movies were big hits.
So the movies are big hits, that are always have return on investment.
Add to the fact that Sony/Columbia do not really own the Spiderman "rights," Marvel/Disney does, but Sony/Columbia have a "leasing agreement" where they have to actually use the rights continuously or they revert back to Marvel/Disney. (Some other companies movie rights have reverted back to Marvel/Disney, Daredevil, Blade, Punisher, Ghost Rider).
Sony will continue make spiderman movies while they make money. Or Marvel/Disney has to renegotiate the contract with Sony and the only way Sony would be willing to do that is if was Sony's financial interest to renegotiate since Sony has the leverage right now, and if Spiderman rights revert to Marvel/Disney you know of course they will make another Spiderman movie.
Sorry Tom, Spiderman is here to stay.