(a)where, by reason of sub-section (2), the, right of any successor to continue in possession of the premises becomes extinguished, such extinguishment shall not affect the right of any other successor of the same category to continue in possession of the premises but if there is no other successor of the same category, the right to continue in possession of the premises shall not, on such extinguishment, pass on to any other successor specified in any lower category or categories, as the case may be;