I disagree....
I think our disagreement is more a disagreement about the odds than an absolute disagreement. This is more specifically what I believe with regard to the chances that Trump will not serve out his full term:
1. Health - Trump is probably less healthy than all of the presidents of my life with the possible exception of Lyndon Johnson. There is a reasonable chance that he will need to resign for health reasons or will be shoved out for health reasons.
2. Mental issues - Trump is mentally unstable. Obviously the Republicans are ignoring this or even hiding it right now but he may reach the point where the Republicans would act to end his presidency for this.
3. Crimes not associated with the election before his election - Trump has committed various kinds of fraud throughout his career. After the collapse of his casinos it appears that he stayed afloat with Russian involvement. It seems likely that there was illegal activity associated with this and that it is possible that this will unravel and be enough to force him out. It could even provide the mechanism for it as part of a Spiro Agnew type agreement where he makes a deal where he avoids jail time if he resigns.
4. Crimes associated with the election - We just don't know how likely it is that Trump will be brought down by this. Lots of people near him were breaking laws but it is a big step from getting the underlings convicted to using that information to remove a still politically powerful president. The Cohen raids may play a role in pushing this forward and they may play a role in pushing before the elections crime investigation and prosecution forward.
5. Crimes while Trump is in office - Obstruction of justice may be the most important. I have no doubt that he is guilty of obstruction of justice, but the political reality is that it is long way from what davefoc thinks he knows to forcing Trump out because of it. Not only are there questions about what his motivations were with regard to the questionable actions, there is the issue that regardless of what his motivations were he had the right to do it. Trump would clearly cross a line if he was shown to be offering pardons for silence. And one of his lawyers seems to have done that but I don't expect that to do Trump in. There are also all the various ways Trump is ripping off the US with the abuse of his office to enrich his enterprises. However, the Republicans have accepted this and it is hard to see how Trump will be held accountable for this. There is also the possibility that a nexus will be found between Trump's decision making with regard to Russia and conflicts of interest Trump has with regard to Russian.
For me the total of all the possibilities above is greater than 50%. Perhaps for you the total is substantially less but unless it is zero our disagreement is not absolute.
The possibility that any of these items will undo Trump are made more likely by various facts that work in the Democrats favor and may lead to Democratic gains. If Democrats get control of the legislature the chances of real investigations into various Trump shenanigans will skyrocket and Trump may be seriously impacted by this.
1. Reduced impact of gerrymandering - it looks like the long term trend is to reduce the effect of gerrymandering which has mostly worked in Republican favor. This makes it more likely that Democrats will be elected.
2. Changing demographics - Trump's main base of support is centered on older voters. They are gradually aging out
3. Trump's tax plan - A tax plan aimed so squarely at making rich people richer is a political liability. The accompanying massive deficits are also a political liability
4. Trump's trade wars - These may be enough to have had negative consequences by the time of the next election and even if they haven't the reality that trade wars will be bad for the US seems to be dawning on the effected people.
5. The corruption of Trump's administration - Scott Pruitt will be a gift that keeps on giving for the Democrats, but the overall corruption of Trump and various members of his administration is a significant political liability.
6. A lot of Republican legislators have already decided not to run thus eliminating the incumbent advantage for Republicans in those districts.