Microsoft have updated their product page for their Xbox One wireless controller with lots of specs, but one that stands out more than the rest.
"Connect up to 8 Wireless Controllers at once to your console."
Re: Xbox One Will Support EIGHT Controllers and Other Launch News
The PS3 already supports 7 controllers apparently. Can't see 8 people playing at once though, although in a Mario Party/All-on-screen clusterf*ck scenario this could be hilarious.