Some think they will die of old age before Littlefoot reaches adulthood. However, if that is the case, then Littlefoot will almost certianly go to live with Bron, as his need to be with his grandparents, as he put it at the end of the 10th film, would be done. If that happnes, he will leave Cera, Ducky, Petrie, and Spike, which would be quite heartbreaking.
One hopeful note, ironically enough, that they might live for many years yet, is the matriarch of Ali's herd, the Old One. She is so old that even Grandpa and Grandma Longneck call her the Old One. So she must be REALLY old. (On the other hand, I've seen old relatives actually call themselves old, so that doesn't necessarily mean anything.)
I personally view that, if Littlefoot had children, they'd live to see them live to adulthood (though I doubt they'd be around too too much longer after that.) .
On the other hand, being a grandparent doesn't mean one is being stalked by the Grim Reaper. After all, Topps is alsoa grandfather. He looks like he'll be around for quite some time. Considering that Topps and Grandpa Longneck might be peers, this speaks good for Grandpa Longneck being around quite a while.
And, considering that Tria, who looks quite young still, is a peer of Topps, she and Grandma Longneck might be the same age. Many fanfics I've seen here have had them die before or by the time he reached adulthood.
Of some comfort is that the odds for them dying before Littlefoot reaches maturity is kind of low as Littlefoot doesn't need to lose any more family members (he already lost his mother and his fahter was AWOL. Surprisied Grandma and Grandpa Longneck didn't blame him for the death of their daughter, saying that if he hadn't decided to go off looking for a better place, and had been the proper husband, taht their daughter would still be alive. Either they showed a lot of restraint and decided not to open that old wound then or they bought his story.). They aren't likely to kill them off in future films.
Still, what is your view?