Correct, it wont cause any harm. Question? Why would you want to do it??????

You would be reading the chip when you perform a write instruction and vice-versa.

Also, although it won't matter, but you will be physically be reading another memory location within the chip itself. Getting a byte out of location 1 of the RAM will actually be a call to a higher memory location. IE, assume 255 locations (8 address lines). An instruction as in

movx a, #01

example will actually read location 128 of the memory chip as A0 maps to A7.

Unless you want to make you code unnecessarily hard to read then DONT switch the IO lines. Just picture it....
Its a dark and stormy night. You are furiously coding away. Suddenly a piece of new code you have written isn't working. Deadlines are aproaching. Finally after pouring over the code for hours, you remember that you switched the IO lines around. Instead of performing a read instruction to read from the memory, you should of performed a write instruction. Great, now it works and you must work through to 4 in the morning to finish it off. Back at work at 7. Get the picture??