Amazon will probably have some very strong competitors. For starters, there will be national-champion types, who will prosper due to geo-compliance issues if nothing else. (I.e., rules restricting cross-border data transfer.) Other security compliance will also matter, both pro- (strong enough security) and anti- (government back doors). OpenStack is currently an Amazon fast follower, but that's apt to change, with OpenStack getting some technical advantages as well. And OpenStack is likely to maintain the very big advantage you can move it among providers and hardware configurations, on-premise or off-.