Salami has been officially sliced. It is now acceptable for current lawmakers to make visits to Taiwan. I'm guessing cabinet ministers are up next before the end of Biden's term.
To be honest, there's nothing to slice. China's red line is that the ROC cannot be declared independent or it will reunite it by force. The US and every other country, even totally powerless nations, have always had the ability to send any people they want, including the president, to the ROC. Just based on civility, China would never have attacked and based on civility (and lack of benefit), most nations had no desire to do it. But recently, as we see, the US has lost its civility, to its allies, to its citizens, and of course to China, because it is a king driven mad by fear of losing his throne to his challenger. So the US is still very much moving in its limited space; it has just simply not chosen to go there before but now, it is desperate to do anything that can be seen as antagonizing China, no matter how useless, because those are all the cards it has left. In the end, there really is no salami to slice; it is a red line: if the ROC declares independence, there will be war. They dare not breach this red line but China will move this red line forward. Eventually, when China is strong enough, the red line will become an ultimatum to reunite or else.