Smiley face tells me it's definitely either a tease or trolling.

Edit: ^^ 0_0

A next gen Jak would be orgasmic.

Maybe E3 clears this up?

That would complete this years E3 megaton trio, but naughty dog wouldn't be working on both crash and jak.

Try them again. 1 was fun but shorter than an indie game, II is a disgusting mess that is somehow beloved because of nostalgia, and 3 is fun but stuck trying to make sense out of what happened in II. 

Also, who's Jack?

The brother of John Shit?

They've mentioned it before, but only in response to someone asking them about a new Jak and Daxter game, to which they've said (paraphrasing) they've moved on as a dev from younger style games, and want to explore more adult experiences.  But yeah, I can't recall them bringing up the subject of a new Jak and Daxter unsolicited.

Thats in your opinion, but there's obviously a large group of people that would welcome a next gen jak game developed by Naughty Dog with what they know now.

And I wanna see Daxter as a witty little rodent in HD.

I'm sure I'll buy a PS4 someday, but if this is legitimately teasing Jak 4, that day will come much sooner.

I'm fairly certain they revealed the canned Jak 4 unsolicited when talking about how TLoU started. To quote Josh Sherr, "it's also dictated by what the market wants," and he then effectively said they'd never go back to Jak because most of the Jak team has since left. Hell a good chunk of the Uncharted team is gone at this point too. Druckmann and Straley's coup has vastly reformed ND as a studio.