I'm not talking a real kiss, just where their lips end up meeting one another by accident.
Are you thinking of "The Lady and the Tramp"? I guess that's the most famous kiss by accident in a cartoon so far.
Considering the target audience, kissing isn't something we're likely to see. A friendly lick, perhaps, but that's it, and I have my doubts on that.. It would be interesting to see a kiss between them, but I just don;t think we'll see much elaborating on the relationship between Ali and Littlefoot.
I agree that there probably isn't going to be anything beyond what we saw already. While the relationship between Littlefoot and Ali is different from any other LBT relationship among the younger characters it is nothing "explicit" as the relationship between grownup characters such as Topsy and Tria. They are just kids. Kids can fall in love, but that kind of love differs from the love between grownups in many ways. One can refer to it as a sandbox love I think.
As for the friendly lick, I think from the LBT character's perspective it may have a different meaning than a kiss. More like a the French bize, the kiss to greet somebody without any whatsoever sexual relation. After all we've seen quite a number of such licks in LBT already, from Spike, Ali (with Petrie being the receiver), Chomper, and Littlefoot's grandma (in which case the purpose was to clean Littlefoot). There was nothing like it from a couple such as Littlefoot's grandparents or Topsy and Tria.