"become a certainty" is correct and usable in written English.
You can use it to describe something that has been confirmed or is certain to happen. For example, "With her hard work and dedication, it has become a certainty that she will succeed in her field."
By the time the statement reaches your friend's friend's roommate's uncle, it has become a certainty, complete with descriptions of forcible haircuts given in the store's tiolets.
Sex in space is thought to have to become a certainty, as it is unlikely the couple on the Mars mission will want to abstain for the entire 16-month trip.
Default on the nation's $500 billion in public debt would become a certainty, depositors would take their money out of local banks and, with a sharp devaluation of as much as 50 percent, inflation would loom.
To threaten us with legal action for doing so will create a system where significant abuse will become a certainty – protection of child rights can only be maintained when clinicians retain our rights.
A congressional resolution authorizing strikes was on life support even without the Russian option; with the Russian option on the table, the resolution is as dead as a doornail buried six feet under in the local cemetery, and the potential humiliation the administration was facing a few days ago would become a certainty if they decided to turn to the offer down outright.
And if underlying pressures are not resolved, it will almost become a certainty by 2007.
Mr. Arnett did not become a regular presence on NBC News and MSNBC until war became a certainty.
Enslaved Africans became more difficult to hold as manumission became a certainty.
That likelihood became a certainty in 1823 when the formation of the Catholic Association transmuted the demand for emancipation into a mass political movement that commanded attention throughout Europe.
As it became a certainty I hoped I'd be lucky enough to put the plays in front of an audience this year.
On Wednesday, as a stimulus deal became a certainty on Capitol Hill, I asked David Axelrod for his take on this Groundhog Day relationship between Obama and the political culture.
