Mozilla is always looking at ways it can improve Firefox and has not shied away from experimentation. However, with the new rapid release cycle, we may start seeing the results of these experiments a lot sooner than before.
One example is a proposed UI revamp, which is only in mockup form now, but which already looks promising.
The aim of the revamp seems to be simplifying the few remaining UI elements, the tab bar in particular.
Some of the notable changes include the removal of the dedicated search bar and the rounded tab corners, similar in a way to Chrome.
In fact, there are a lot of elements that look similar to Chrome's, but it's not really a rip-off, the proposed Firefox UI has a lot of details and elements that put it ahead of Chrome in terms of functionality and especially looks (although the latter isn't saying much, Chrome has never been much of a looker).