The new Littlefoot looks fantastic!

While your previous attempts were still great drawings, this one is a vast improvement in terms of making Littlefoot look older. The angle is great; I love how you did the legs and the neck; even the ridge on his spine looks perfect.

Regarding your concerns about his face, I personally think the size of his head looks just about right (and you shouldn’t make his eyes any smalleróif anything they should maybe be just a teense bit bigger), but perhaps you could make his muzzle slightly longer. Not only would make him look more mature, but I think it would look better.
The only other thing I would change about him is his tail. It looks too thick, and not tapered enough at the tip. I wouldn’t touch the tail’s upper side; the way the top of his tail connects to his body makes it look like it is realistically merging with his spine, and that looks good. I also like how you’ve made the edges of the dorsal “stripe” wavy along his tail (compared to the earlier drawings in which they were straight); to me, that gives the impression that Littlefoot is larger and has more “room” for patterning detail (no pun intended). And despite its thickness, the shape and position of the tail look very good; the curve is very smooth, and the way it is held up implies a lively and still youthful character: the Littlefoot we all know and love. If you wanted, you could make the width of the stripe a little narrower, but the wavy edges are something you should definitely keep. (Should part of the paler “belly stripe” also be visible on the underside of his tail from this angle?) Anyway, if you’re going to decrease the width of the tail, you should whittle it down from underneath and from the right.
I hope this doesn’t sound too harsh, but to be perfectly honest, I think your previous image of an older Petrie looked better in most respects. In that version, the top of his beak (above his nostrils) ended at about the same level as the tops of his eyes, whereas here it is slightly lower. It doesn’t merge with his forehead as much, and somehow I don’t think it looks as good. Also, his head looks rather bulbous here; it seemed to be lower and more streamlined in the earlier picture. And I don’t think the point where his chest meets his stomach doesn’t need to be as pronounced (Both it and the ruff around Petrie’s neck looked just right in the earlier picture, I thought). The biggest issue, however, is that the line of his stomach no longer curves down to his left leg, so there is much less of an indicator that his left leg is in front of his right. As a result, his legs and lower body look much more two-dimensional, and very strange. I would strongly suggest reinstating that line.
Okay, now for the good news: Petrie’s legs (apart from the aforementioned detail) and wing membranes look very good in this image.

You pulled off the capelike look of his wings excellently, and furthermore you added those little lines in the corner of his left wing that indicate stretching or flexion of the wing membrane. That’s one thing this image has over its predecessor. The other is the shape of the legs. The knee and ankle joints are much more clearly defined, whereas in the earlier version they looked kind of shapeless. And the feet and toes have much more dimension to them than before.
Speaking of feet, I personally think Petrie might look a little odd with claws on his digits in the manner of Pterano’s, especially since his hands and feet are much darker than the rest of his body. However, his fingers and toes (fingers especially) might benefit from being made slightly thinner and more pointed, with more obvious joints. Also, perhaps the dividing lines between his toes could extend further back along his feet, to give the impression that his toes are longer.
Personally, I’ve always liked the idea of Spike remaining voluntarily mute his entire life, maybe uttering an occasional word (or a few words) if it’s really important. As for Petrie, I’ve sometimes envisioned him as having improved grammar as an adult, but lapsing into his juvenile speech pattern when he’s panicked or excited. Alternatively, maybe you could have him talk the way he did in the original movie, using “I” and “the”, but still leaving out linking verbs.