More likely streak of 3 winning elections for prez?

[President Johnson]

The second option is far more likely. In the possible but unlikely event Trump wins again, I expect 2024 a Democratic landslide at least as big 2008 (President Gretchen Whitmer?).

I think the 2020 might be a redux of 1980: Unpopular incumbent president who ran as an outsider last time gets ousted by his charismatic or elder challenger (Biden or Kamala?), though it won't be a ten point win or 489 electoral votes. The new president implements reforms that change America for decades and easily wins reelection to a second term over a party that has trouble to put together a winning coaltion. Even though the ecomony was laggering at some time, it is good enough for the sitting vice president, who is less inspiring, to win over another weak opponent. He or she gets unpopular over his/her term and in 2032 loses to a more moderate opposition. (Something similar also happend with Hoover/FDR/Truman/Ike).