Mesh networks unfortunately scale really poorly [1]: O(1/sqrt(N)). You really need a fat backbone to turn the topology into something more like a hypercube.
[1] https://pdos.csail.mit.edu/papers/grid:mobicom01/paper.pdf
[1] https://pdos.csail.mit.edu/papers/grid:mobicom01/paper.pdf
In practice who knows what kind of communication patterns you would get. Applications would probably evolve around the long distance limit if it existed, but it's hard to imagine not having backbone links. Most likely the meshes would stay relatively localized (and I believe there exist a number of regional wireless mesh networks out there serving real customers).