This is a grand jury indictment for prosecution rather than impeachment due to the Senate. I say by the end of year, setting stage up for prosecution upon his leaving office in 2021.
That is how I see it. When a prosecution of the President becomes moot, this investigation will itself be in the winding-up phase with the activity in Federal courts. I see President Trump losing to a Democratic nominee who gets 295 to 375 electoral votes. with him gaining nothing from 2016 and losing Michigan, Pennsylvania, and Wisconsin with near-certainty; and Iowa and Arizona with a high level of certainty. I see the President having about as much chance to lose Texas as to win Arizona, and the states on the bubble are Florida, Georgia, North Carolina, and Ohio along with the recently-wayward Congressional Districts of Maine and Nebraska. That is the margin of the electoral vote that I see in 2020, and I cannot distinguish those four stat4es and two districts as well as I can distinguish them from Arizona and Texas.
There are other possibilities -- flight, disability, death, resignation, and the now non-zero chance of a military coup.
Of course there are others who will be at legal risk. So far members of the House and Senate have yet to be exposed.