Yes. You can download them now while they are free, then immediately remove them from the iPhone. When you actually want the free app in the future, go back to the app store as if you intend to purchase it for its normal price. The app store will recognize that you already own the app and redownload it at no cost. I have done this in the past and as far as I know things have not changed. I think this may also work for music purchased via iTunes on your same account. Please let me know if I am wrong.

If you want to be safe, download and sync with iTunes then remove from the iPhone. The app will still be saved on your computer within iTunes and can be reloaded onto your iPhone without any need to communicate with the app store.