Scalability--not so much. If you were really interested in building a highly scalable service (5M+ concurrent users) you probably would want to look at a different tool/language. But, chances are, Django works just fine for your initial/early use cases (before what you're building goes "viral" lol) and for most web app use cases on the internet. Duplication--yes. If you are talking about duplicating project boilerplate, Two Scoops gets into this topic specifically (using a neat package called cookiecutter). If you mean replication (e.g., horizontal scaling via replication of instances of your app), then that's more of a dev ops thing and depends on your deployment setup. I would suggest digging into literature about AWS, or whatever PaaS you choose.
1. Versions -- both books target Django 1.8+ (Django 1.9 is the current, stable release), so I would consider both relevant for now.
2. I suggested both books because both are current and different. Django By Example includes examples of projects beyond a simple blog (I think that's chapter 1 or 2). Each chapter introduces more and more complexity with a totally separate project example. Whereas, Two Scoops of Django provides general recommendations for how to best manage common Django tasks/flows. I think both are appropriate for intermediate/advanced users.
