St. Paul says it's conditional on continuing in the faith. I think he's right. What do you think?
Paul was employing a first class condition:
"The first class condition indicates the assumption of truth for the sake of argument. The normal idea, then, is if--and let us assume that this is true for the sake of argument--then...." (Daniel Wallace, Greek Grammar Beyond the Basics, p. 690).
The believer can never lose his salvation and perish:
"For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life" (Jn.3:16).
Do you really think that those have received the truth in power and in the Holy Spirit can ever stop believeing?:
"The elder unto the elect lady and her children, whom I love in the truth; and not I only, but also all they that have known the truth; For the truth's sake, which dwelleth in us, and shall be with us for ever" (2 Jn.1-2).