Do not make this mistake that I almost did.
You can go ahead and roll your Traditional 401K into an IRA without any issues and it has better choices, more options for getting your money in various payouts you can customize. You can also do nothing, just leave it until your ready to do something with it.
BUT DO NOT DO THIS....If you have a ROTH 401K- do NOT roll that into a Roth IRA......you are better off leaving it where it is. WHY? The 5-year clock RESTARTS when you open a new ROTH IRA to roll your money in. My advisor almost had me do that. I questioned it thank god. If you re-start the 5-year clock because you opened a new ROTH IRA for a rollover, you will not be able to withdraw any gains tax free ( you can withdraw the principal tax free) until 5 years from now. For those needing money that they don't want taxed or added to their yearly income, the ROTH is a good vehicle to stay under your goal max incomes for tax purposes and use for things like health insurance til your 65, unforeseen expenses, etc. So I'm suggesting, if you have a ROTH 401K, keep the money there. At Verizon, they allow you to roll the traditional 401k and still keep the ROTH 401k there. Good luck to all and as a former employee under 65, life has been great since leaving.