We can't say either way we can only speculate with a high probability of being correct in regards to devil fruits regenerating or coming back after the user is deceased.
As an example we can see that in romance dawn it states the "gomu gomu" tree regrows every 50 years; sure this was before oda conceived the idea of a unique fruit per person instead of just a rubber man, it is very interesting.
We could just dismiss that as oda being indecisive and will change that later, however characters KNOWING what a fruit is before eating it is a very very strong proof that fruits need to come back in some way or form.
However, oda could surprise us all. What I myself want to know is why in flashbacks that date back hundreds of years no devil fruits are around...
This leads me to a theory but it's premature. As an example; the one shot Oda made called "Monsters" is actually canon to One Piece story, in fact that is where Ryuuma came from, he is the main character still alive in that story. Not only that but the Wano country is a new world country, so devil fruit powers should not be that uncommon. This can easily be explained due to oda doing this before one piece and couldn't of included it but still what if this is a hint? Same with Montblanc "Liar" Noland, why did no one in his timeframe have devil fruits that we know of? That takes place 400 years ago, monsters probably takes place between 200-800 years ago.
For some reason I believe devil fruits may not be an ancient thing, in fact it's so weird that so many fruits exist, but in the four blues most people regard them as a myth.
We know at least devil fruits date back 50 years, and since brooke was not hesitant about eating it probably existed longer back then that. Though to our knowledge devil fruits originate in grand line which could explain why four blues regard them as myth. However even marines get surprised when they see a fruit user.
Regardless that's the bigger mystery, we can say we a high probability that fruits do grow back however.