I think the bit of WGTs database that holds the number of friends you are allowed, can only hold a maximum value of 255 (one byte), so unless WGT change that to hold a bigger value, we're going to be stuck at 255.
one byte = 8 bits (binary digits)
8 bits = 11111111 (binary number)
11111111 = 1x1 + 1x2 + 1x4 + 1x8 + 1x16 + 1x32 + 1x64 + 1x128 = 255
Do you wish you hadn't asked? Lol. ; )