I know Futureshop leaked Sleeping Dogs, LBP Karting, and a hint at GoW: Ascension two years ago on Twitter, but I'm pretty sure they got in trouble, so nothing leaked last year.
Last year, though, everything was on lockdown because of PS4, so I don't know if they even had anything of system there since all that happened before, and the rest of the platforms had a fairly quiet year. This year, more stuff should be ready to talk about.
However, yes, it's a retailer show, not a press event so don't expect huge news (especially since they often don't treat news as huge to even the people there, it's sometimes a blink-and-you-miss-it announcement for something that GAFers might lose their minds over) unless something cool leaks.
Actually, you can unfortunately expect a lot of bullshit around that time too. Because nobody in the know can go, but then the odd store clerk will go as somebody's representative (or at least that used to be the way, I don't know the attendance of this show these days?), you get wild and unverifiable rumors that sometimes lead to something and sometimes are total bunk.
They did announce at the 2009 Destination Playstation that LittleBigPlanet, Motorstorm and Assassin's Creed games for PSP, so hopefully we hear about at the very least a Drive Club release date, or some Vita 3rd party ports...
They announced LittleBigPlanet Karting at the 2012 Destination Playstation. And officially announced to the public on March 22
Public announcements? No. LBP Karting was part of a flier that was leaked from the event, I don't remember the timing of any of those PSP announcements, but as far as I know, Sony has never "announced" anything to the general audience during Destination PlayStation. It wouldn't necessarily be bad timing, though, those B-tier games (they generally save AAA for E3) that they showcase there have got to go out at some point and stuff might leak from that show anyway. I'm not sure if part of the allure of Destination PlayStation is seeing things ahead of those who don't attend (there's other business done there too, that's its primary purpose actually, but as with a lot of things, much of this could be done digitally these days without having to have bookers fly across the country,) but out of the games that have leaked from that show, I feel like there's not a lot that needed to be kept exclusive. LBPK waited a month before it fully showed itself, for example, unless the build/trailer wasn't ready I couldn't tell you what they gained in waiting?
GDC news is probably developer related like someone already said. Free Unity for example.
GDC will have that kind of stuff, but no, whoever does the keynote especially will treat it as a game showcase and not just as a tech wonk. Remember that Killzone 2 and LBP were both shown at GDC.