Sony has registered a pair of trademarks with the USPTO.
“Entwined” and “Kill Strain” were filed for on April 14 and April 15 respectively. And on April 17 and April 18, the two names entered the Trademark Reporting and Monitoring System.
Entwined and Kill Strain are both intended for use of a game software. More specifically, the two trademarks pertain to “Computer game software; Downloadable computer game software via a global computer network and wireless devices; Video game software”.
It could be possible that these names are new games that Sony will reveal soon. At this point in time their is no evidence that suggests anything else about this, however Kill Strain somehow leads me to consider that this could be something to do with Killzone but at the moment it is impossible to say for sure. Entwined could then be just about anything, but give the name it could be something quite incredible and meaningful. For now we just don't know but if Sony has any current plans for the two names will probably find out more around E3. Though if Sony wants to use these for games I feel they really should put some work into the Vita and give it some quality exclusives to get people to buy it and these possible games could be the key.
Source: Gaming Everything