What if the president gets a bad flu?

@Riley12 So long as Trump is mentally competent and able to speak on January 20, I am extremely confident he will take the oath and that will be an inauguration - even if it happens in doors and isn't followed by a speech. If Trump dies before the 20th, then Vance gets inaugurated on the 20th and that is still an inauguration. The only two scenarios I can think of where there isn't a presidential inauguration on the 20th are these. If Trump is in a comma, then he can't take the oath, but Vance also can't ascend to the presidency, so I believe Vance would be inaugurated as Vice President and immediately become Acting President. Or, if both Trump and Vance die before January 20th, then there is nobody to inaugurate, the Speaker of the House becomes Acting President on the 20th, and we have an inauguration whenever the Speaker/Acting President nominates and the Senate confirms someone as Vice President, who would then immediately become President - or, you know, the Speaker never nominates anyone for Vice President and just serves the whole term as Acting President. All of these scenarios seem extremely unlikely.

@RiverBellamy no the speaker would become the permanent president and no longer be a member of the house.

@datachef No, there is no legal provision for a person other than the Vice President to ever actually become President. Below that in the line of succession people can only act as president. See https://en.wikipedia.org/wiki/United_States_presidential_line_of_succession, or https://www.law.cornell.edu/uscode/text/3/19.

I just looked through the legal provisions, and you are right that the Speaker, on becoming Acting President, would have to resign his speakership and his seat in the house. And in the scenario where the Acting President appoints a new Vice President, I am now unsure whether that Vice President would become President or not - seems like murky and untested waters.