While LoL does already have basic AI-controlled bots, those in the new mode are said to be "more challenging and complicated," using tactics like ganking and defending key map areas. The selection of champions the bots can play will also be expanded.
Furthermore, players will gain more Influence Points and XP in the new co-op mode than they would by simply beating up on helpless bots in regular custom games.
Co-op vs. AI mode is due to launch "soon," whenever that is. And How Soon is Now?