Tricky. Since Loki didn't survive the events of Ragnarok according to Norse mythology, there are some that did. Like the Nidhogg, which is currently a popular guess for his devil fruit. If he has that, he will be alive.
But if his devil fruit is another creature that didn't survive, it's owari da.
(Just kidding I know that Oda won't just copy 100% from myth and apply it to his Story)