How do Software Developers stay current on the exploding "polyglot" databases and web frameworks space?

I agree with Glenn. That is work with one set of technologies which completes the whole stack of web development from data base and backend web framework to a Front end MVC and maybe even a CSS framework. I think Once you know and understand a certain stack of technologies which is capable to delivering a full fleged application, then basically you are capable of delivering a web product, which is the overall point of all these technologies. Also only when you understand a certain stack of technologies to a level of detail, so that you can deliver production ready application, then it will much easier to dwell into other technologies and swap few layers in your preferred tech stack with something new. At that stage you will know that you will be needing a certain set of function in a data base ORM or ODM when working with db and a OOP language. Also you will know the differences between the technologies that you considering to use to suit you special need for a new application. personally, i am working with the node.js platform and the whole ecosystem around it for testing and automation. On the database side i am working with mongodb (mongoose) and neo4j (node-neo4j), and Backbone.js for the front end MVC.