Once you are established in your middle voice you have access to a very wide repertoire of songs. As you work to both higher and lower portions of your range, outside the middle voice range, you will no doubt be working to eliminate any bridging artifacts thrown up by moving through to medium and low chest or into the upper registers.
There is no 'plateau' at either end of the voice. As your middle voice blend gets smoother, you will be carrying blended voice both downward and upward. Right to the very bottom, where you may previously have thought 'chest' you will see that when you sing 'connected' all the way down, there is always an open passage to the head resonance.
At the top you will soon extending buzzy resonance into the very upper notes, giving a chest-like brightness and complexity to the sound.