Nah, they're going to update both games at the same time graphics wise. Saves them a lot of work. And from the time when I still played, they kept making graphic updates.
Runescape has a lot more paying members then a lot of better looking mmorpg's. What you say doesn't make any sense. Yes, PCs will get better over time and they will slowly update their graphics, but they would make a lot less money if they decided to have graphics on par with WoW for example.
You'd think people would have learned by now(this gen as main example) that good graphics is not really important.
Jagex earns a big sum of cash through ads on their site. 10 million people visiting your site regulary= lot's of cash through ads only(If you're f2p in runescape then you're forced to see ads while you play lol)
They're also intrested in the ps3/xbox360/wii by the way, so perhaps you'll see some retail games of them in the future.
