a No universal manifestation occurs unless a previous dispensation reaches its maturity. At the time of Baha'ullah's claim, the Bayan as a dispensation was only between 13-18 years old and its first Mirror was only in the 13th-18th year of his ministry.
b The anticipated timespan of the Bayan was to be similar to other dispensations, which means a duration of 1000 years and above.
c The Bab provides the numbers 1511 and 2001 as the years of this timespan until the Promised One of the Bayan appears.
d The Bab anticipated the erection of 18 shrines to the Letters of the Living and one for himself as the 19th before the appearance of the next manifestation.
2 The Bab anticipated a system of continuing hujjiya where 19 consecutive mirrors would appear every 66 years.
3 The Promised One of the Bayan is supposed to be the archetypal "return" of the Prophet Muhammad (ص).
4 A Babi or Bayani state is anticipated before the appearance of the Promised One of the Bayan.
5 The Babi/Bayani laws and ordinances would be implimented before the coming of any next manifestation.
6 All the writings of the Bab (and his successors) would be collected and printed before the coming of the next manifestation.
7 The Promised One of the Bayan would be born to human parents at an unspecified date in the future, would have a childhood and attend school and grow to adulthood. Baha'ullah was already the Bab's senior by 2-3 years (the Bayanis celebrate the date of 1820 rather than 1819 as the year of the Bab's birth).
8 The Bab addressed Baha'ullah as an inferior and only as 238 (the numerical value of 'Husayn-Ali). He never bestowed on him any titles, and the title baha' itself was given to him by Qurra'tu'l-Ayn at the gathering of Badasht in 1848.
9 The Bab claimed his ontological identity with Subh-i-Azal in several key tablets, in one particular one addressing him as "You are I and I am You."
10 Baha'ullah paid public obeisance and reverence to Subh-i-Azal for 11 years per the Bab's instructions.
11 Baha'ullah whitewashed while plagiarizing much of the Bayan with his kitab-i-aqdas being a totally distorted version of the Bayan with the addition of a few nonsensical ordinances by himself (such as the laws pertaining to marriage, inheritance, arson, etc). This raises legitmate questions as to what the need would've been to abrogate the Bayan if one was merely going to rehash and plagiarize it. Note that even the concept of the house of justice was not uniquely Baha'ullah's. This was first enunciated by Subh-i-Azal in his 1852 Book of the Testament (kitab al-wasiya).
12 Baha'ullah's writings and his overall teachings are not particularly profound. They are rehashes of Persian Sufism but popularized with a vague Babi afterthought and all put under the rubric of a very authoritarian form of modernism.
13 Per Arabic Bayan 9:11, the Bab unequivocally leaned in the direction of an eco-socialist order where the buying and selling of the 4 Elements are prohibited (something the world desperately needs presently) whereas Baha'ullah fully sided with Western Anglo-Saxon capitalism. In other words, Baha'ullah sidestepped the real solution and instead plunged headlong into the problem.
14 The Bab repeatedly stressed the sanctity and veracity of the four gates to the Hidden Imam, and in his sahifa 'adliya unequivocally states that whosoever dismisses them is a heretic. These four gates are believed by the Bayan to have "returned" as four of the Letters of the Living. The Bab also believed in the physical existence of Muhammad ibn Hasan al-'Askari (ع). Baha'ullah instead called the four gates to the Hidden Imam (ع) liars and did not believe Muhammad ibn Hasan al-'Askari (ع) physically existed. In fact he sided with al-Shalmaghani, whom the Hidden Imam (ع) cursed as a heretic during the minor occultation, as well as Ja'far the Liar whom he called "Ja'far the Truthful." This makes Baha'ullah fundamentally a heretic from the point of view of the Bab and thus automatically negates any other claims he made.
All in all, Baha'ullah's enitire claim rests on quicksand. There was literally no anticipation of an imminent universal manifestation to abrogate the Bayan until the elapsing of this abovementioned 1511 to 2001 year interval. The only anticipation of manifestations was that of the consecutive mirrors of the Bayan, the first of whom was Subh-i-Azal.