Assalam O Allaecum Could it is possible that one gain so knowledge of Quran and hadithes that he becomes fifth Imam

1) There is no indication in the Qur'an and Hadith that there can be only four Imams. However, the four well known Imams were authorities in their field. They had dedicated their lives in gaining an indepth understanding of the Shariah of Islam. More importantly, they successfully managed to document and codify the Shariah : thus enabling the ordinary person to easily practise upon the Shariah.
There were many other capable scholars, however, with the passage of time only these 4 schools of jurispudence gained prominence. One should understand well, that becoming a mujtahid or an Imaam is no simple task. There are certain basic requirements before one is conferred with the title of a mujtahid or an imam.
A scholar who :-
a. has gained full expertise in all branches of Islamic knowledge such as Tafsir, Hadith, Fiqh, Arabic and their related sciences;
b. has deep-rooted insight & understanding of the goals and objectives of Shariah;
c. has the keen ability of extracting principles from the Quraan & Sunnah and then being able to infer verdicts from them; and
d. is extremely pious and sincere in his teachings.

Since these 4 Imams possessed these requirements they more than adequately analysed and synthesised the Shariah. Consequently, the need for a 5th or any other Imam does not exist.

2. The Muftis of current times are merely transmitters of the views of the Mujtahids of the past. They themselves are not mujtahids. Their task is to merely study the works of the 4 Imams & provide appropriate solutions to contemporary problems based on the deductions of the Mujtahiddeen of the past.

and Allah Ta'ala Knows Best

Mufti Ebrahim Desai