We have known about the existence of the Phineas & Agent P figures for a while but now we have some interesting news via Toys R US. According to the Toys R Us website, there will be a Phineas & Ferb Toy Pack which features Phineas & Agent P figures along with 2 power discs (which will not be included in Series 3, so are exclusive to this toy pack)
The figures Phineas & Agent P also look to be available as single figures.
According to the website the Toy Pack with the figures & power discs is set to be released on 04/01/2014 with the two figures set to be released on 04/29/2014. But obviously this could change.
Here are the images of the packaging for these figures and toy pack which confirm that these currently look to be Toy Box only characters.