Personally, I hope that they go through the Battle Zone after the league, and encounter Heatran. Below is what a possible plan could be, but what will not be done in the anime. Just what I would like to see happen.
After losing to some random trainer, and placing in the top eight in the Sinnoh League, Ash, hearing about the Battle Zone, drags Dawn, who lost to somebody in the Grand Festival, and Brock, the only character aside from Ash to make it through every season, to compete, however, Paul is competing as well, and is still a jerk, causing Ash to confrunt him, and lose again. So Ash and his group then wander around the battle zone looking for the Frontier Brains, or whatever they are called in Platnium. (I never competed) But some random villain decides to awaken Heatran, in order to cause an eruption. And while Ash obtains the third symbol, this threat emerges for the first time, and after that is a fight with Paul. Ash looses again, due to his pokemon being tired from fighting off the villain. Eventually, Ash discovers Stark Mountain at the exact same time the villain decides to act, and while the villain does indeed meet Heatran, Ash somehow calms the legend down, pissing off the villain who is eventually captured, or has realised his mistake. (But I doubt someone intent on causing a volcanic reaction to destroy everything on the island will learn from them... but I might be wrong) And Ash obtains the other symbols and beats Paul before going back to Johto to compete in the league, or to stop Team Rocket's plans which were leaked by the incompatant trio.
But while I know this is completely and utterly wrong, it is something I would like to happen.