That just means you've got an extra four months to file your return. It doesn't give you any extra time to make your payments.
It's better to file, even if you can't pay it, than not to file at all.
The bottom line is this: The worst mistake you can make is to do nothing. Either file a return or get an extension request in, but do it by the deadline. Sitting back and doing nothing is going to cost you a lot more if you owe taxes.