Mobile vendors won't mind because your phone will say "5G" in the status bar and they can charge more. But in reality your phone to web-site performance (particularly outside of artificial benchmarks) may not improve substantially.
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.
Considering multiple carriors would each have 20gbps and there are ~200,000 cell towers in the US we are talking massive bandwidth in aggregate.
I actually think the home market would be an ideal place for them to start, as its much less 'mobile' so if you get coverage, your not going to have spotty coverage while they fill in the gaps.
https://newsroom.t-mobile.com/news-and-blogs/uncarrier-tv-cl...
You can see that they evaluate LTE at 50Mbps, which is around what Verizon phones were getting when they first started going to market but before congestion and backhaul limitations were hit due to the number of LTE devices on the network.
Currently on LTE with AT&T, I can usually hit 10-20Mbps, so applying the 14x ratio, I'd expect to be able to get 100-300Mbps with 5G once congestion takes hold, which is quite sufficient.
Which is going to put a lot of pressure on ISP's to improve.
I've been under a "provider" who caps out at 10Mbps with, sadly, about 40% uptime with our neighborhood for about 5 years (constant outages. On a first name/you've got my phone number basis with the contracted technician, as is quite a few people in the neighborhood). I joined the board to get out of it. We're due to get out of it at the end of March, but Spectrum has zero interest of coming in and servicing people. CenturyLink said they'd be willing... but want a 5-7 year contract and everyone in the neighborhood is understandably against that idea.
So yes, bring on the time when mobile bandwidth is such that low caps aren't "needed" and the speed is high enough to get rid of ISPs as an option.
I was originally with Verizon, but the pricing was a bit steep so I left (grandfathered unlimited data plan, but was paying pretty heavily for 2 said plans).
I switched to Sprint and that was working fine, their unlimited data plan was working and the prices were much cheaper. However, the previously mentioned fiasco with our ISP meant that tethering was now important to me as a fallback when needed and Sprint's plan didn't include tethering and it was a bit steep at the time (as a developer, I have to work on things at night sometimes from home and garbage internet won't suffice there. I empathize heavily with the people in the neighborhood who work from home constantly/online classes, I do).
So I switched to T-Mobile with the Simple Choice plan at the time with basically same features, but 14GB tethering per line and added two more lines for the kids at a reasonable rate. January I switched to the One plan and added International Plus (unlimited tethering) and I predominantly tether now and only connect to my actual router that leverages the garbage ISP when I need to use my internal network (and I check the internet at that point and it is still bad). Plus, tethering is typically 3x faster than said ISP. Needless to say, I absolutely love T-Mobile in our location, it isn't great everywhere though from what I hear, and it works fine for me as an outright replacement (I don't do Netflix or other streaming from computer, so my tethering isn't particularly damaging. Plus, not in an area of high congestion).
So there's a ton of difference here: I've been able to move around as needed to get what works best for me when it comes to the cell phone company side of the equation and I've been hamstrung with the ISP side of things. Plus, I don't even dislike Verizon and Sprint, they work well, but it just didn't work for my needs. With ISPs and the limited competition, they have little incentive from their peers to make me like/accept them, case in point the ISP we're stuck with until end of March.
For example, when multiple good links are available, Multipath TCP will tend to flip flap between them rather than stabilise on one or the other. You can also get massive reordering which will tend to throw off the congestion control algorithm, but I believe that issue has since been resolved. Good chance are there are some other issues that make MPTCP not quite suitable for widespread use right now.