As you know, each country must keep their power stable, otherwise they'll be at the risk of being attacked by other countries, as it was clearly stated after orochimaru's invasion arc back on the first mangas. Konoha is by now the weakest of the ninja villages and had some major loses. When other countries know about the situation, an invasion is imminent and it doesn't sound good for them. And, kishi interview said that right after pain's fight there will be a great war.
