It may happen but most likely it would be labeled as a port first since the s4 or s5 most likely have a few different things hardware wise or software wise
Also cyanogen is built directly from android source code cm11 is android 4.4 they just added there stuff to it, and tweaked the code around, one of the reasons a stock ROM usually never performs as good as a custom one
According to the screenshots I've seen online from an electronics show the s3 was labeled to start getting 4.4 march-april, so by the end of this month you'll hopefully get some news on it
Whether or not we get an official one may be up to virgin mobile tho, they can actually decline the update in which case no one would have an official VM version
Or they can even purposely block it as they did with my previous device
My previous device was a triumph, when I purchased it originally from VM main site it had the badge that said will be upgraded to gingerbread, that never happened, after some research online I came across an article stating android contacted VM multiple times and told them a single piece of there software was all that was stopping the update so if they were to change it they could roll out gingerbread
VM response was nah we ain't changing it, which cause the triumph to officially stay on froyo even tho the phone itself wasn't released by VM till gingerbread was already out and ice cream sandwich was actually just rolling out as well lol