If you are still abroad on 10/15/17 after filing form 4868 you can even get a further extension until 12/15/17 by send a letter containing the required information to the IRS.
Filing late is not necessarily bad since many believe it reduces your chance of an IRS audit. The IRS of course will not comment onf these theories. Have questions? Email firstname.lastname@example.org or go to www.TaxMeLess.com