If you're in the scanner and long press on a portal you'll now see a new option to 'Hack No Key', and this will let you hack the portal and not receive a key. Now, whether you'll sacrifice if you would've gotten a key to get extra items... that's yet to be proven.
Also, when you glyph hack a portal, you'll be presented really quickly with a 'command channel open...' prompt. You'll have 2 seconds to enter either the "more" or "less" glyph. This will tell it to hack with or without key options. If you choose more, it'll get you a key (I have yet to do this and not get a key yet, but more testing might be needed to confirm) even if you have one.
This will definitely be more practical than having to drop a key, or place it in a capsule, before hacking to try to get duplicates of the portal key you want.
In my mind this only means more and more links are about to start flying, and is also probably in response to the recently released key lockers, you needed an easier way to get as many keys as possible to fill it, right?
Thanks to +Fev Games for their cool animation showing you how to enter the command (it took me a few glyph hacks before I noticed the prompt).