In applying the rule against perpetuities to an interest in real or personal property created before October 1, 1989, limited to take effect at or after the termination of one or more life estates in, or lives of, persons in being when the period of said rule commences to run, the validity of the interest shall be determined on the basis of facts existing at the termination of such one or more life estates or lives. For the purpose of this section, an interest which must terminate not later than the death of one or more persons is a life estate although it may terminate at an earlier time.