These are the outcome permutations.
(1) Mueller could indict Trump. Trump could be pressured to resign by Republicans under threat of impeachment and do so.
(2) Mueller could indict Trump. Trump could resist pressure to resign by Republicans and no impeachment happens. Trump becomes the first sitting President to stand trial. The country navigates an extremely complex legal morass.
Scenario (A) - the litigation somehow occurs relatively quickly, within Trump's first term.
-> If found guilty, and still President, Trump must be impeached to be removed from office, which would be procedural.
Scenario (b) - the litigation proceeds slowly.
-> Trump continues to exercise the powers of President while indicted since there is no impeachement or resignation.
-> Trump either wins or loses re-election in 2020, while indicted. Winning continues the above, while President. Losing simplifies matters greatly, as a new president gains power.
(3) Mueller could indict Trump. Trump could resist pressure to resign by Republicans and be removed from office.
(4) Mueller could decline to indict Trump, and refer the matter to Congress, that pressures Trump to resign, and he does so, rather than face removal.
(5) Mueller could decline to indict Trump, and refer the matter to Congress, that pressures Trump to resign. He refuses and is impeached.
(6) Mueller could decline to indict Trump, and refer the matter to Congress, that pressures Trump to resign. He refuses and there is no impeachment. Republicans let Trump get away with it. America's legal institutions are shattered by this outcome.
(7) Mueller could conclude that there is not enough evidence to either indict Trump or refer the matter to Congress. Investigation terminates and it gets no further than (let's say) Jared.
(8) Donald Trump could declare victory and go home ("I drained the swamp and beat the deep state, now over to Pence to rebuild"), saving face, just like is important to Russians.
(9) Donald Trump could have a "medical emergency" that necessitates his resignation, just like something out of the developing world.