I think the real reason user numbers haven't grown as rapidly as expected could be the difficulty introducing it to a new user.
I've tried to explain how powerful it is, how it centrally gathers so many diverse publications, how it gives a new perspective on global events or political sensitive topics.
But it's a blank screen, the welcome wizard is helpful (I started with Apple and Google collections and quickly added Planet Gnome and Mozilla), but it's not the same.
Google+ is a product that tries to do everything, but makes the simplest things difficult. After Buzz, Google made discovery impossible, so G+ users accumulate very slowly. I'd like to "subscribe" to a circle, say Linux kernel or Node.js developers, but instead I have to get linked to someones G+ from somewhere like here and then follow just that user. I should be able to subscribe to that entire circle with one click, and have it appear as a subgroup on the left sidebar, and the, Presto, we have 50% of Google Reader.
I would suggest Reader be replaced (if it must) with G+ Curator, a reader for feeds including RSS and Atom, but also G+ Circles, third party feeds like Twitter or Tumbler (if possible), mayabe Google Groups or even a gmail filter.
I would use the Reader API for this, it's basically an atom feed aggregator, and could convert all those other inputs into Atom feeds the same as it does Atom and RSS today. I would translate the current feed IDs into G+ ids.
The problem with Google dropping RSS is it basically kills the prospect of sites bothering with RSS, they look to Tumblr and the like and think there's something there, but they find they can't easily browse other feeds, and it becomes like Facebook (now), a mess of pithy sayings and 'viral' photographs that people probably don't bother to read.
Then, at some point Tumblr (or some other site) shuts down and the community goes with it, the orgranization is lost and the users find something else to waste their time on.
But really, unless Google looks at fixing problems with G+ and makes it something that people want to use, we'll be not talking about it's shutdown a year or two from now