A devise, bequest, or appointment in a will validly executed under the provisions of this chapter may be made in form or substance to the trustee or trustees of a trust in writing executed by the testator or any other person or persons prior to and in existence at the time of the execution of the will, and identified in the will, whatever the size or character of the corpus of the trust (including an unfounded life insurance trust, although the settlor has reserved any or all rights of ownership in the insurance policies). A devise, bequest, or appointment shall not be invalid because the trust is amendable or revocable, or both, by the settlor or any other person or persons; nor because the trust instrument or any amendment thereto was not executed in the manner required for wills; nor because the trust was amended after the execution of the will. Unless the will provides otherwise, the property so devised, bequeathed or appointed shall not be deemed held under a testamentary trust, but shall become and be a part of the principal of the trust to which it is given to be administered and disposed of in accordance with the terms and provisions of the trust to which it is given, including any amendments, as it appears in writing at the death of the testator. In the event of complete termination of the trust prior to the testator’s death, the devise or bequest shall lapse and the appointment fail unless the will directs otherwise.