[Update 4/21/11] Though the device is being discontinued in Japan and Europe, America apparently plugs onward. Joystiq reports that an SCEA spokesperson has said they are "continuing production of PSP Go for North America." So there you go.
[Original Story] Following yesterday's report, Sony has confirmed that it is ceasing production on the PSP Go to Japanese site AV Watch (via Kotaku). A spokesperson said the company is now focusing production on their next handheld, the NGP. Whatever stock remains of the PSP Go will be sold until it's depleted.
If you'd still like an older PSP-3000 model, it sounds like Sony plans to continue manufacturing it for the time being. "It will continue to be sold, and we will keep focusing our attention on it from here on out," said the company.
It's not particularly surprising that between the two models, Sony would let the PSP Go die first. Despite being the newer model, it didn't spur on new sales, and publishers haven't always chosen to put their UMD titles out day-and-date on the PlayStation Network. RIP, PSP Go.