Well, dear reader, I'm glad you asked.
To put it simply, FNaS 1 is basically complete and FNaS 2 is in the final stages of completion, while FNaS 3 has a small amount of progress and FNaS 4 and 5 haven't begun yet.
Here's some previews of what's been done so far:
FNaS 1's... default art border? (Border artwork done by @AlimedelStar 
):
FNaS 1's Extras Menu:
FNaS 1's Gallery, featuring some new stuff visible:
FNaS 2's Custom Night Menu:
FNaS 2 Extras Menu (with some new options you might wanna take note of...):
And finally, FNaS 2's Gallery, once again with something new visible:
I plan to do monthly updates for progress on the collection as I'm doing with my other project, FNaS: Solar Switchup. I know a lot of people are a bit underwhelmed by the supposed scale of the project, but trust me when I say this is more than just a recode that fixes a few bugs. There's some new stuff, returning scrapped stuff, and more waiting for you to discover once the updates for the games release.
Lastly, these updates read and write to the original save files of the games, meaning you won't lose any progress by playing the updates and you can freely choose to play the old versions and switch at anytime!
