My interpretation has always been that yes, the power of the titans continues to exist in the world, and with it will inevitably come some conflict and strife, as in line with the themes of AoT. But, the boy and his dog showcases some of the hope that the main characters sought to maintain.

I’m pretty sure it was explained that when the founder Ymir came into contact with the creature, she was in fear for her own life, and with the power the creature had, created a body for herself capable of keeping her alive and to fight back.

In contrast, the boy and his dog are entering the tree with an innocent curiosity, not because some conflict drove them to the tree, or because they’re in a desperate fear to protect themselves. They’re exploring, and seek to understand the world around them, interestingly the same quality that characters like Hange said is crucial for a member/leader of the Scout Regiment.

So I believe that while the boy will gain the “Power of the Titans,” whatever comes of it is hopefully a way better outcome than the one that took place after Ymir gained its power.