Speculations can begin now 
The most frequent question in chats so far has been whether or not the next sequel will refer to the TV-series (specifically if Ruby and Chomper are to be in it).
Seeing that the last sequel was produced after the series chances are that they may mostly ignore the series (same as with the series and movies on how to train your dragon).
In any case I would think it very probably that they will continue to make "stand alone" sequels as in them not requiring any knowledge of the other movies (the only sequel so far where knowledge of earlier movies was helpful (though not compulsory) would be LBT 5.
Nevertheless I would say there may be a chance that the next movie might refer to the TV series for a different reason. Thing is that possible plots within the limited space offered by the prehistoric setting of a "society" of dinosaurs with survival, food and security being the main motivators are sparse (no doubt a reason that fanfictions usually mix LBT with elements that would be off limits in the movies).
Now the TV series opened up a lot of questions which would provide some good plot material for stories that wouldn't be a mere repetition of what we have seen before. So personally I think it might be possible.
I agree with those who hope that the new movie doesn't continue to focus on the youngest audience only (which I'm afraid was a main cause for the disappointment many expressed about later sequels and LBT 13 in particular).
My personal wish would be for the movie to somewhat return a bit more to the somewhat darker setting of the original or the early sequels (which were far from dark but at least there was some real sense of threat when sharpteeth were around, unlike in case of any sharptooth after LBT 9).
Not quite. Though I actually saw II first, if you don't see the original, you don't know some things.
I did think of one sequel idea that might work (I have several, but I'm gonna put one here.)
Pternao returns and eventually, Petrie starts to really like him again, I don't think, even after seeing his uncle's darker side, that he really disliked him, as he is brought up a few times in the TV series.
Well, anyway, at some point, Petrie and Pterano are doing really well. Then, after a conversation, Pterano drops a bombshell: Petrie's father was one of his followers and died as a result of his "leadership".
Petrie's father has never been shown and this could be a good reason to show why and develop a plot out of it.
Petrie would go really south with Pterano after that, though eventually Pterano would save Petrie's life, say in some fight with some bad guy, possibly Sierra, at the end, and the two would reconcile.
The film could be about forgiveness and all of that.
Here's another possible theory for 14. It would sorta contradict the narrator of the 2nd film, but, heck, Ruby (and possibly the Domeheads) kinda already do.
An omnivore villain sneaks into the Great Valley. He and some of his fellow pretend to be leaf eaters and trick everyone. They are planning to eat lots of leaf eaters, as their mixed diet leaves them undetected.
However, Chomper, and possibly Ruby, who still might be hanging there hiding from Red Claw, somehow overhear the bad guy's plans. The bad guys soon figure this out, kill someone (no, not one of the main characters or their relatives!) and blame it on Chomper, the "evil Sharptooth", causing him, and possibly Ruby, to be run out of the Great Valley.
However, near the end, before the bad guys, who decide, for whatever reason, to go for Littlefoot and his friends first, reveal themselves to be bad, though they have Littlefoot & co. cornered so it looks bad, but then Chomper and Ruby happen to sneak back in and fight off the bad guys, who fall into sinking sand (haven't seen a bad guy die that way in LBT yet, have we?).
Chomper is cleared of all charges of wrongdoing and everyone apologizes to him. He and Ruby are hailed as heroes.
My theory three is that , perhaps Red Claw is revealed to be Sharptooth's brother, and, maybe after a nasty attack in the Great Valley, Littlefoot, perhaps out of anger and spite for that family, goes after him, and is tagged along by Littlefoot and the others, including Chomper and Ruby.
Along they way, they get a group of Sharpteeth and leaf eaters and maybe a Fast Runner or two to all join them and be friends.
Eventually, they come across Red Claw, Screech, and Thud, and defeat them, with Thud, who seemed somewhat redeemable as he was nice to them once, possibly going rogue against Red Claw and joining them.
This sequel theory actually makes quite a bit of sense as that was their aim in the TV series, to get the creatures of the Mysterious Beyond to work together and overthrow Red Claw and his minions.
