Only if Trump wins. If Trump loses then he goes back to being a Senator.

Sure. But someone will be the GOP nominee in 2028. Even if Trump loses, Vance has significantly elevated himself within the party. His debate performance against Walz helped rehabilitate his political stock, and being a sitting Senator is not a terrible place to launch a campaign for the nomination. Being on the national ticket in 2024 also gives him a chance to build a national presence and infrastructure, and to do a lot of appearances for state and local pols. Even if Trump loses, I think he's in the top tier for the 2028 campaign. He might choose not to run, of course - nice to hold a Senate seat in a red state - but if he throws his hat in, he could do well.

Meanwhile, De Santis probably won't be in elected office leading into the 2028 nominating cycle. He's term limited, so he can't run again in 2026; and neither of our Senate seats will be up for election in 2026, so he can't try to move into that spot. I don't think he's too strong a candidate in 2028 regardless of whether Trump wins or loses.