It may be a question of debate that Google's decision to discontinue Orkut is Good or bad because it is still widely used in India and Brazil. Still we have give farewell to first social networking site on 30 Sept 2014 when finally discontinued from the web. for more latest update on Orkut - see this End of era in Social Media and ask at least once that this how much this Google's decision can justified
Without knowing the internal workings of Google its hard to understand this decision. Its not like Google+ is this runaway success story.
I doubt that they will take the decision likely, also given the fast pace of the Internet and the diverse views of its users, it is often better to look into the corporate strategy and make the decision themselves.
According to me it's right decision. They have some audit report of orkut to take this good decision.
Google is directly competing against Facebook so investing into 2 social networks is only going to make things more difficult and lengthy for success. Competing against yourself usually is not good . Besides, Orkut did not get an update for a couple years now so that should have been a hint that it wasn't in Google's long term plans.