but the decision could fall to Trump, who has opposed banning TikTok.
I firmly believe he only ever said that to get elected. Trump is the one who called for the ban in the first place, and he's already shown that he won't be following through on the campaign promises he doesn't actually care about.
Members of his previous administration complained about his tendency to just kind of agree with the last person who spoke to him on a given topic / day. I assume it's mostly due to his love of (need for) flattery - he comes out of each meeting feeling great and wanting to endorse whatever that person was saying.
There are legitimate security concerns in having large numbers of your citizens using a platform that directly controls algorithms to show specific content, run by a foreign company known to have direct government control, force them to do what they want. TikTok may deny it, but Chinese law allows the government to essentially force them to do whatever they want. And yes, that includes the US and other countries as well, this is not a US or China thing, it's a general foreign narrative control issue.
Nothing prevents the Chinese government from forcing TikTok to adjust their algorithm to promote whatever points of view they want and suppress others. Many other countries do the same with their own companies, whether overtly or not, but a foreign government that is known to do what they want, regardless of any agreements, treaties, etc. having the ability to directly control what your citizens see is a massive security risk.
Is a full ban the right approach? The US doesn't really have any way to force TikTok to ignore Chinese government demands, it is a Chinese company after all. The only way to force compliance, is not allowing them to operate in the US as the alternative, and the company can choose to either do what the US government wants, or abandon the market. It seems that's the stage the politicians have decided we're at, and TikTok hasn't made changes to accommodate US requirements to operate here anymore.
Quick, everyone jump over to one of the other massive data-harvesting short-form content apps with ties to the US government. You like freedom and Hummers parked inside the mall, right youths?
You would WANT to use that shit? It is awful. Curious why you feel the need to have any social media at all? I get setting up private groups, chats, etc on your own hardware. But corporate made algorithm driven and profit centered applications out of your control seem like a horrible idea. And it turns out they are.
That assumes the main reason it exists (in the US) is to be the platform it is.
An alternative is that it's meant to be a way for the Chinese government to control the content and thus any narrative they want US citizens to see and interact with. If that's their actual goal, then selling it and losing control doesn't do anything for them.