By including the classic Tommy and Kimberly (they go hand-in-hand because that is one on-screen romance that we will never get tired of) the franchise hands itself off to a new generation of heroes to inhabit these roles in a way that feels incredibly poetic.
Their cameos in the film are also important because, as the director points out, the ending of the movie teases future storylines for Tommy in the newly rebooted series.
The entirety of Dean Israelite’s Power Rangers seems like a significant passing of the torch moment for the franchise, and the appearance of the original Kimberly Hart and Tommy Oliver helps reinforce that idea.