that "a president is immune from criminal prosecution for any official act that he takes as president even if that action is taken for an unlawful or unconstitutional purpose". 

Trump claims that if the president does not have immunity from prosecution, that future presidents will be indicted by the opposing party:

Is there any truth to this? Will conservative AGs start pursuing indictments against Dem presidents?

I will count any past/current/future US President from the Democratic party, and any indictment that alleges they committed a crime while they were acting as the President. So, indictments that would have been prevented by "Presidential Immunity" if that were the law.

If an indictment like this occurs, all remaining options in this market resolve Yes. If it does not, each time period resolves No as it arrives and the market close date will be extended.