Traditionally Capital One has not offered anything when you attempt to cancel your card (a retention bonus) but reddit user eacip0 reports they were offered a $200 Capital One travel credit when trying to cancel the Venture X card.
Obviously this is only one data point so I’d be interested to hear from other readers to see if this is a change in policy and if it extends to other cards or only the Venture X. You can read our post on retention rules and tips here.