A lot has changed since tabulous was released over five years ago. Neither Twitter Bootstrap nor Ember.js had been launched yet and people would look at you funny if you talked about "hamburger menus".
Tabulous' vision has always been to make it easier to manage tab-based navigation within the paradigm of server-side rendering of web pages. But in today's world, it's much more likely a web application has a dynamic, responsive menu bar than a simple row of tabs.
Because of this, future support for tabulous may wane. I would not suggest using it for a new project unless you are fine with the limitations of server-side rendering.
I plan to support all of the minor versions of Rails 5.x but it's possible that tabulous will not support Rails 6.
Wyatt August 6, 2016