There are no circumstances – nor set of circumstances – under which President Buhari may seek to amend the Constitution regarding the two-term term limit on holding office as President.
President Buhari intends to serve his full second elected term in office, ending 2023 – and then there shall be a general election in which he will not be a candidate.
There is not even the faintest possibility that this will change.
It is important to note that there was a past attempt to change the Constitution to allow for the-then incumbent president to stand for a third term. That attempt was wrong, unconstitutional – and rightly rebuffed. No such attempt will happen under this President.
President Buhari is a democrat. He respects the Constitution. Any activity aimed at altering the two-term limit will not succeed and shall never have his time nor support.