This is more complex than that...

Actually SMS is being replaced to some degree by mobile-based instant messaging, including push notifications, which provides some new features and are much lower cost. Many of the 4G LTE networks don't yet support SMS despite being from the same mobile operators.

Expensive IPv4 blocks mean that the price of hosting a website on IPv6 is cheaper, or getting IPv6 access via broadband, so ultimately this will have an effect. A similar example: the price difference between Windows and Linux web hosting is one reason why Windows only has about 20% of the market there, which illustrates this can happen despite switching costs. The price difference per month is only a few dollars for Windows vs. Linux but it does have a market impact, and totals to a big impact on Microsoft's potential revenues.

Going IPv6 on a webhost is not that expensive initially - they must ensure the OS is configured OK on the servers they start with, and provide a 6to4 tunnel to someone like Hurricane Electric. That's all endpoint configuration and can be the end of phase 1 - only once they get customers on IPv6 do they need to look to a native IPv6 end to end with an IPv6 upstream, which can be phase 2 once they have IPv6-driven revenues. Much easier to make the business case.

Ultimately the customers of webhosts will decide - if they get more problems with IPv4 due to NAT, they will ask their webhosts for IPv6, and some of them will switch to hosts that do provide IPv6.