The Republicans, perhaps PDJT, should DEMAND the opportunity to cross examine the whistleblower because they have evidence that Schiff and his staff helped write the complaint.
The president has no authority to do so and the Pubs in the house have no authority to do so. The rules in the house are whatever the majority party decides to do.
It's anybody's guess if the Pubs in the senate will demand to cross examine the whistleblower, and it will be easy enough for the Rats to tie up any subpoenas in the courts for months or years.
The whistleblower will never testify.