Islam "is" a religion of peace should really be phrased Islam "will be" a religion of peace - for as soon as all the world is under the dominion of sharia law, and those opposing islam are subdued, there will then be peace!
Peace is the ultimate goal of all totalitarian factions. Getting there by any means - deceit and violence included - is noble to the outcome!
Even that I find hard to believe, because the biggest killer of muslims in muslim countries is other muslims. There are nasty sectarian conflicts within islam in countries that are solely islamic.
Muslims murder muslims every week around the world. There will never be peace when muslims are involved. It is against their religion.
More likely scenario is that Islam ... will be ... pacified.