Update: According to NegativeGamer.com, A4T's licence manager Angela Jones stated it was a “mistake on our part” so for the time being it appears the PSP-4000 will remain only as speculation.
Today TheLostGamer.com (linked above) reports that a LittleBigPlanet PSP case ad by Accessories4Gamers Ltd. from MCV UK's digital magazine (Page 17) hints at a Sony PSP-4000 console on the way.
This news appears to further confirm previous PSP 4000 rumors of it's existance.
To quote: "Whilst we've only really seen a whole range of Sackboy figurines on retailers such as Play.com, we've picked up an advertisement displaying an upcoming LittleBigPlanet branded PSP Case and includes a set of stickers for you to customise it.
The advert, from Accessories4Gamers Ltd., details that it is suitable for 1000, 2000, 3000, 4000 and PSP Go models too... wait... 4000?! Uh oh, seems like someone has maybe confirmed recent rumours too soon!"
More PlayStation 3 News...