The intervention creates an incentive for provoking governments to commit large-scale atrocities by launching armed rebellions against them. This isn’t going to guarantee future interventions, but it may help create the conditions for future massacres. For many reasons, Western powers are not always going to be so quick to intervene, but the Libyan intervention creates the expectation that other governments will feel compelled to step in if the rebels’ situation is dire enough.
That is likely to encourage rebel movements that are militarily and politically weak and have little chance of succeeding on their own, but which are just strong enough to create a crisis that will lead to calls for another intervention. We can’t know how much political instability and violence the implied promise of future interventions may cause, but it is a horrible precedent to set.