The phrase "a wave of speculation as to" is correct and usable in written English.
It can be used when discussing a surge of conjecture or uncertainty regarding a particular topic or event.
Example: "There has been a wave of speculation as to the reasons behind the sudden resignation of the CEO."
Alternatives: "a flurry of speculation about" or "a surge of conjecture regarding".
As the new rules became clear, a wave of speculation emerged as to how Slim's companies would react.
The report set in motion a wave of speculation in media as to whether the invention might be some revolutionary type of computer or some sort of personal transportation device that functioned like a hovercraft.
The lack of information prompted a wave of speculation about what happened to Mr. Goldberg, who was well regarded as an entrepreneur and mentor and was the less famous half of one of Silicon Valley's most prominent power couples.
The 26-year-old's social media activity, spotted by the Evening Standard, prompted a wave of speculation among Spurs fans on Twitter as excitement continues to grow over the possibility of Mauricio Pochettino landing the DR Congo international.
There has been a lot of speculation as to where Apple's next wave of growth is likely to come from – with rumored product lines including electric cars and streaming TV services.
The sudden death of the supreme court justice Antonin Scalia has prompted a wave of speculation about who might replace him as one of the nine justices.
Stuart Lancaster has resigned as England head coach, triggering a wave of speculation over who could replace him in charge of what is set to be a completely revamped national coaching team.
That report set off a wave of speculation that the rogue nation was undertaking clandestine cyber warfare to coincide with its missile tests over the weekend.
News of the availability of quarterback Jay Cutler set off a wave of speculation Wednesday, after the Broncos revealed the night before that they were willing to trade him.
Those words unleashed a wave of speculation about Mr. Ridge's future that continued until Mr. Bush selected Dick Cheney as his running mate and that began anew last month with talk of Mr. Ridge as secretary of defense.
