But I don't think strtok will work with a string that is not zero terminated, so you may need to find another way of parsing the array.
It will, but the results will not be what you expect. Somewhere in memory, after the address that is the start of the array, there will be a NULL. strtok() will keep processing until it finds it. The NULL is its clue (as with all string functions) that it has reached the end of the array.
If you really are too lazy to increase the size of the array by 1, and to NULL terminate the array, that's fine. Simply do not use any string handling functions (strtok, strcat, strcpy, atoi(), etc.).
Really, learning to deal with NULL terminated arrays of chars will be quite useful in most everything you do with the Arduino, and is worth taking the time and effort to learn how to do it properly.