Yea theres a couple of gaps every once in a while when it comes to Midtown. Remember, Midtown wasn't always tall towers. It started out as low/mid rises and eventually taller towers grew. In the future these are bound to be developed.
https://www.google.com/maps/@40.7626..._R8IMzjA3A!2e0
Lots of smaller structures amongst taller ones.
Example:
https://www.google.com/maps/@40.7598...ixu_NkwBzA!2e0
Or:
https://www.google.com/maps/@40.7603...ArG1MTzr_A!2e0
Hopefully these get developed.