"What you'll probably see is more of the competitive type: more maps, more modes, stuff like that. The co-op stuff is hugely time-intensive and the size of it - the physical download size - is huge, so that's probably not an option.
"I'm not going to say never," he added, "but for the foreseeable future we're not going to be doing that."
Richmond admitted that he is "fascinated" by co-op, and that there is stuff he would "love to do next game" now the code is in place.
"Naughty Dog does a really good job of defining things, and I think no one's really done a definitively amazing amazing co-op experience and I think we can do that, and it's something that at some point we'll tackle," he said. "If I have my say, then that's what we'd do."