Depends!
(With reference to the title and the OP)
IF they have just repented and confessed all the sins they have committed since the last time they have repented and confessed every sin - before they have a chance, to move, think or breath, and they die - then they are still saved and going to heaven.
IF they have NOT just immediately done the above, then they have obviously lost their salvation, and will have to sit the rest of eternity in hell wondering why they weren't repenting/confessing 24//7 and if maybe those people who believed in eternal security, who were not to be seen anywhere in hell, were right.
(Just being snarky - God, of course, is the only judge! But the above has always seemed like the logical consequence of Arminianism and the false doctrine that a believer saved by God, can lose his salvation (or gain it!) by what he does, or does not do!)
PS. Not saying we don't live for Christ and obey his commands. That goes with the joy of knowing Christ, abiding in him, and walking with him daily!