The correct answer to "what is the maximum size of the array?" is "lots:" it will depend on the size of the elements (an array of bytes can have more elements than an array of 1 MByte MPEGs) and how much memory is available at that time.

To answer your specific question: it will probably easily handle those 50,000 names, but this is also tending towards the neighborhood where using a database will be a Good Idea.