Upto 211 degrees, nothing happens. At 212 degrees, water boils.
Similarly, will 1 good show make a lot of people subscribe to Netflix? Even if the show is orgasmic - I doubt it. There is no momentum here. No tipping point. 2 shows won't do it either.
I don't know what the minimum number of new shows is that would get a lot of folks to subscribe. But for myself, I would put it near 12 or so.
If Netflix wanted to reduce their risk, they should have targeted niches that are not so expensive. Mainstream entertainment is not a good idea to start with. Something like History channel or World Travel is.
But going with low risk niches, would not generate so much publicity for them. Would not make the studios and cable companies take notice. Netflix is in a fight with them - and so this is a strategic move to get noticed. Not a risk reduction move.