While my 401(k) is thankful, I'm wondering how much longer this can go on. Obviously the stock market got a big boost due to the tax cuts which lead to companie

While my 401(k) is thankful, I'm wondering how much longer this can go on. Obviously the stock market got a big boost due to the tax cuts which lead to companies repatriating a bunch of overseas profits, but what happens next year when there's a lot less money to bring back?