The phrase "are increasingly sure" is correct and usable in written English.
It can be used when expressing a growing level of confidence or certainty about something over time.
Example: "As the evidence mounts, we are increasingly sure that our hypothesis is correct."
Alternatives: "are more confident" or "are growing more certain".
Eden seemed to be doing well, and her parents were increasingly sure she would soon get her second Keytruda dose.
In the exam room, he seemed without normal communication skills; I was increasingly sure that he was on the autistic spectrum.
Officials here privately say that they were increasingly sure that a North Korean attack sank the ship, which killed 46 sailors.
Senior intelligence, military and national security figures told CNN they were increasingly sure the plane had been the subject of a terrorist attack when it broke apart over the Sinai desert on 31 October.
There are costs: judicial review leads to more paperwork, for instance, because civil servants have to be increasingly sure that they have followed procedures precisely as laid down in the statute.
Mr. Zakaryayev said he ran into Mr. Tsarnaev repeatedly at a Salafi mosque in Makhachkala, Dagestan's capital, and was increasingly sure he would not join an insurgent group.
Barcelona forward Lionel Messi says he is "increasingly sure" that he will never play for another European club.
"I'm increasingly sure that in Europe, Barcelona will be my only club". Messi, who is with the Argentina squad preparing for the 2018 World Cup in Russia, started out at Newell's Old Boys before joining Barcelona aged 13. "The other day I was talking to a friend and he told me 'if you had chosen Spain, you'd be a World Cup winner already', but it wouldn't have been the same," added Messi.
But he was increasingly sure that he didn't like sex with women, and the Viagra that his father gave him on two occasions only made him feel worse.
With economic distress widening and school budgets tightening, many districts are increasingly focused on making sure that enrolled students belong in the district.
