To kick it off, I'll give you my current prediction, and rationale.
The good news is that if you believe my prediction here, you can get at least 50x your money on the prediction markets right now.

My pick:
Donald Trump Jr.Here's my rationale for this pick:
1. Donald Trump, even today, has absolute control over at least 50% of the GOP primary voting base.
2. Donald Trump cares about one thing: Donald Trump. He does not care about the USA. He does not care about the Republican Party. It is better for him to be the leader/influencer of a diminished party than an outsider of a more powerful one. (It is important to emphasize just how
drastically different this is from previous presidents).
3. Because of these two things, Trump will be in a position to select the next Republican nominee for President. He controls 50%, and he can credibly threaten the remaining 50% that he will obliterate the party by running a third party candidate if they don't do what he says. (This is how he won the nomination himself last time).
4. It will be in Trump's best interest to have somebody he
absolutely trusts as the GOP nominee. He will need somebody in the presidency who can pardon him and his family, and defend against the lawsuits and fines he will undoubtedly suffer if somebody he does not trust is in the White House.
5. Trump absolutely cannot trust any "normal" Republicans. There is a saying in Washington in the Trump years that the only politicians who hate Trump more than the Democrats are the Republicans.
6. The only one Trump can truly trust are his own family members. And the only reason he can trust them is for the same reason mob bosses can trust their colleagues: they are part of the criminality and thus he has leverage over them.
7. Therefore, Trump will choose his oldest son, Donald Jr. (I say this over the others since he's deeply vested in Trump's grifting ventures, and he's the most public of the family members--but this can change and perhaps it can be Eric or Jarrod as well).
8. Since Trump has absolute leverage over the party, the nominee will be Donald Trump Jr.
It's early days, se let's see how this ages

. In particular, it will be interesting to see which of the assumptions above hold up, and which turn out to be wrong (if any!).