In many cases, the company that bought your company will just move your 401(k) over to its 401(k) administrator, and you'll continue to pay into the account as you did before. In other cases, your account may be kept separate for a time. You might need to open a new 401(k) account with the new employer and roll the existing funds into that. If your plan is terminated, you can still roll over your funds into an IRA.