Trump has refused to say what he'll do because threatening Social Security during an election would cost him a lot of votes from seniors. On the other hand, now that he has won, Republicans have started freely admitting that Project 2025 is the plan for this administration. Project 2025 has this to say about Social Security.

Project 2025’s 900-page Mandate for Leadership fails to propose any solutions for Social Security and says, on page 710, that its proposals for the program could not be “covered here in depth.” Notably, that line was co-authored by economist Stephen Moore, who has advocated to slash and privatize Social Security, once calling it a “Ponzi scheme” and encouraging students to burn their Social Security cards. Kevin Roberts, the president of the Heritage Foundation, has also gone on record to say the Mandate for Leadership manifesto is just the basis of their plan and “there are parts of the plan that we will not share with the left.” Last month, his organization called for raising the retirement age, and the author of that analysis, Rachel Greszler, is listed as a Project 2025 contributor.

I would hazard to guess that the incoming administration will, at the very least, try to raise the Full Retirement Age to 69. I will be pleasantly shocked if they don't try to privatize it as well.

He's promised not to touch it. But this guy's not gonna fix it either.

Too early to say, but assume Social Security and Medicare/aid are fair game.

The conventional wisdom is that Social Security is a so-called "Third Rail" of politics. Nobody is going to touch that and live to tell the tale.

Of course, we would have had a similar thought about non-controversial stuff like "cooperating with the World Health Organization," so there are no guarantees, but wholesale restructuring of the program would (hopefully) cause more backlash than any politician wants to deal with.

The blueprints he's working from doesn't say anything about SS by name: https://www.newsweek.com/what-project-2025-could-do-social-security-1923892

Despite being over 900 pages long and spanning most of the departments of government, including defense, homeland security, agriculture, education and energy, the mandate text does not provide direct policy positions on Social Security or its government agency.

That's not to say the program will be entirely unaltered, but that page suggests the extent of the (public) policy proposals seems to be raising the retirement age by a few years. Not great, but nobody seems to be loudly advocating for slashing existing benefits.

He has stated he wants to make social security tax free