> how many towers currently have the bandwidth capacity at their base to support this new throughput at scale? All this may do is shift the bottleneck

Expanding tower capacity is part of the 5G build-out. There's an upgrade spending binge going currently. The US wireless market has enough competition now, mostly thanks to T-Mobile, to force all of the carriers to properly upgrade. They're not wasting any time, all of them are aggressively pursuing it as a competitive advantage.

AT&T and Verizon have been losing customers to T-Mobile for years now. If they make the mistake of claiming 5G, when it's not, T-Mobile will just use it as an opportunity to hammer them. Competition, it works.

This also gives the large carriers in the US an opportunity to go after taking more broadband business from Comcast.

Most sites have fibre backhaul now. And then point to point wireless can do 10gig+ these days anyway to a tower that does have fibre backhaul.

Even with fibre, it wouldn't take many users on the theoretical capacity of 5g to saturate the uplink.

5g is shared bandwidth from ~20Gbps download 10gbps upload, increasing the number of users over a minimum does not increase peak bandwidth just utilization.

Considering multiple carriors would each have 20gbps and there are ~200,000 cell towers in the US we are talking massive bandwidth in aggregate.

Another factor to add though is that traffic likely won’t increase by 14x at the same time. Apps will mostly finish payload transmission earlier, leaving the connection unused for a longer period of time. So there likely won’t be as many concurrent transfers in a cell as there are now.