Q: Shouldn't this list contain the speculated Trump-Ukraine scandal whistleblower?
A: No. Wikipedia will not include the name of any whistleblower, alleged or confirmed, including the speculated Ukraine whistleblower, until it is the subject of non-trivial coverage in reliable independent secondary sources (RS). Inclusion in RS is a necessary but not sufficient criterion for inclusion. To understand what Wikipedia means by reliable in this context, please review the list of perennially discussed sources. Note that partisan websites - left or right - are not acceptable for contentious claims about living people.
Q: What about X?...
A: The inclusion criteria for this list were set in a 2013 RfC: any person may be listed, provided there is an article [here on Wikipedia] about the whistleblowing event. Optionally, their name can be piped to the event to provide consistent blue links. Subsequent consensus holds that an article on a scandal, without a specific article on a whistleblowing event related to that scandal, is generally insufficient.