Mature electromagnetic gun, the traditional main gun has too close range and poor accuracy. The key to BB's comeback is to have a mature electromagnetic gun capable of launching gun-launched missiles. This can basically be achieved in the next 50 years.
A powerful air defense system, similar to the air defense system combining laser and missile, can effectively intercept aircraft carriers.
Electromagnetic gun and laser are both big power consumers, so the requirements for shipborne power supply system will also increase.
An effective reconnaissance system, BB itself does not have much reconnaissance capability, so it is necessary to monitor and communicate satellites in real time.
Of course, after the above points are realized, it is not ruled out that the development of space technology will make naval vessels more miniaturized.