No,It always was the idea of playing with a lot of other people on the same world that drove me to runescape. I loved the vibrant atmosphere with lots of people around you all doing different things. Its something that is missing a bit in the current runescape.
Maybe there should be less worlds,so that the worlds that are there are a bit more bussy and lively.
Take it a step further, if there were no more updates, and all the prices remained the same I would play EVERY bit of content in this game with no restrictions. As it is now I can do what I am comfortable with and not risk losing tons of GP to the markets or anything else. I have great patience and no desire to compete, so today's billion dollar weapon will be nearing alch price when I finally gain some interest in it.
My GE history and legacy-only gameplay would tend to confirm this.
The main attraction of RuneScape is the community, well parts of the community. So downloading a single player version of it would be utterly pointless.
I would just move on from the game if it came to be point of offline/ downloadable version as so much of the game would feel broken which was designed around many players working together and the social aspect that helps you form going insane with the grinding aspect.