The problem with RS3 and mobile is the graphics. Even if they release the full version of OSRS for mobile doesn't necessarily mean that RS3 will be following close behind. Phone graphic's are a pain to work with on most games that have good graphics to begin with. The way it would be right now if they brought out the beta for RS3 would be that the graphics would be similar to that of Runescape back in let's say 2002-2003 pretty much the same what OSRS graphics. So it doesn't matter when RS3 mobile comes out, it will come out in beta soon enough when it's ready and not a moment sooner.