> Taxpayers' answers are then translated into standard tax forms and transmitted to the IRS's Modernized e-File (MeF) API, which is available for authorized public use
The interoperability with the revenue system is provided by a different project, and this API is also used by turbotax and the like. It won't be going away.
It could easily go away, if there are claims of people abusing the API, or using "unlicensed software to use the API" causing errors. By licensed, I mean "approved to use the API".
There could also be pushes to monetize the API, "Why is this service free!?". Meaning they'd likely require a need to be incorporated, setup a commercial account with them, and have payment method on file, and on and on.
My point is, I can think of dozens of sneaky ways to make that pesky API go away, and I'm not even trying.
The interoperability with the revenue system is provided by a different project, and this API is also used by turbotax and the like. It won't be going away.
The interoperability is not the hard part.