Bringing back RSC would be an insult to all the players that have had their accounts wiped with the removal of the servers. They should make the game open source or something and just release it so people can do what they want with it.
As for bringing back Classic. No thanks it's long gone and best left gone. Was good in the days but the bots settled in and took over. Very few people played. Do you want even more bots playing Classic selling goods on websites. I don't think so.
Bringing back RSC probably isn't worth the investment on Jagex's side. It's also hard to deliver RSC as a stand-alone product (in the form of an application that could be run on your own device, like an offline RSC Hardcore Ironman of sorts), as Jagex isn't very open to sharing the server technology behind the game (which is very reasonable).
That said, there are a lot of RSC art assets that Jagex could possibly just put under a public license, so anyone interested in using them for their own projects could do so without concern. Given how Runescape as a whole started as a small project by a bunch of brothers, it'd be a nice legacy if those very same RSC assets could play a part in the foundation of someone else's projects.
In any case it would be a better fate than it all being abandonware.