The phrase "ample speculation about" is correct and usable in written English.
It can be used when discussing a topic that has generated a lot of conjecture or theories.
Example: "There has been ample speculation about the reasons behind the sudden market fluctuations."
Alternatives: "plenty of conjecture regarding" or "a lot of theories about".
These advisers said that although there had been ample speculation about Mr. Rove's seizing the reins of the Republican National Committee, he was almost certainly headed for some sort of special advisory position in the White House.
All the along, there's been ample speculation about whether Facebook was building its own mobile phone device, or as the company has publicly hinted, how it would integrate social layers into different mobile operating systems and platforms.
There has been ample speculation, informed and otherwise, about the sale: how much the team is worth; how much equity the owners — Fred Wilpon and Saul Katz, who are heavily leveraged — really have in the team; and how much they will be able to raise without selling control or letting the buyer have some say in financial decisions.
Her sexuality has been the subject of ample speculation in recent years, though she has remained mum about her personal life.
There had been ample speculation on how he had been brought back.
There was ample speculation from attendees regarding just how significantly these changes will impact our industry.
But that has left ample room for speculation about how the people came to be in the house that night and what happened there.
As the novel opens, Brian, Arthur and Avril are en route to her surprise 70th celebrations, providing Brian with ample opportunity for nostalgia-filled speculation about what might have been had the seductions of Highgate not claimed him.
Any speculation about causation?
Speculation about next year's N.B.A. draft?
That has increased speculation about her plans.
