Looking for a specific transition for Adobe Premiere
This may get down-votes since it's so manual and doesn't have perfect video quality, but I'll offer it anyway.

CREATING THE GENERIC TRANSITION


Bring 30 clips into a project.
Shrink the scale of all of them.
Drag them onto the timeline so they're all playing at the same time.
Position them in a grid.
Export that project in the best possible quality you can.


CREATING THE SPECIFIC TRANSITION


Open the generic transition video in a new project. Place it on the timeline.
Bring in the 2 videos you want to transition between.
Shrink their scales, put them on the timeline, and position them over 2 of the existing videos.
Export that project in the best possibly quality (matching the generic clip).


USING THE SPECIFIC TRANSITION


Import that specific transition into your project.
At the end of the first clip, place the specific transition on the timeline.
Animate the motion of the transition: Start with the scale zoomed in on the "starting" video. Scale back to 100% while moving the clip to center the "ending" video. Scale up (zoom in) on the "ending" video.
When the "ending" video fills the screen, cut the specific transition.
Add the actual "ending" video to the timeline. Trim the left end of the clip to match the right end (last frames) of the clip in the specific transition.


I haven't tried this but in my mind it should work really well.  The video quality will be a bit lower during the transition, but it may not be noticeable - especially in lower-quality environments (like web video) or if the transition is brief (1-2 seconds).