UPDATE: Polyphony Digital has now confirmed that GT5's online servers will be shut down on May 31st 2014, not May 20th as stated in the original article.
Gran Turismo 5 will no longer be playable online in 2014.
The news comes as part of an online shutdown for several of Sony's first party games, including the Resistance trilogy, SOCOM and MAG.
GT5's onlline functionality will be shutdown on May 20th 2014. GT5 will of course still work offline, but it's a different story for SOCOM and MAG – these games were only playable online, so will therefore be completely obsolete. A full list of affected titles can be found on Sony's online support page.
You could argue this is a not particularly subtle way of urging people to upgrade to Gran Turismo 6 – a similar practice that EA is often accused of.