Depends on whom the Democrats will run in 2020. If they run someone like Bernie Sanders, Tulsi Gabbard or Nina Turner caring about the issues most people care about, issues like universal healthcare, tuition free college, re-regulation of wall street, a more peaceful foreign policy not threatening nuclear war, etc. then they will probably win against Trump.

If they run someone like Hillary, Oprah or this Joe Kennedy who held the official Dem-response to Trump's State of the Union then they will lose again because these people are not caring about these issues and also stand for a warmongering foreign policy (atleast we know that from Hillary and Oprah, but I'm not sure if this Joe Kennedy also falls into the neocon warmonger-category). Unfortunately it currently looks like the Dems will really run someone from this category again. At least the corporate Dems want to do that.

I think the only hopes to avoid a 2nd term of president Trump are either grassroots-groups like Justicedems successfully taking over the Democrats or a successful 3rd party running against the Dems and the GOP.