I think it’s safe to say this deal has been in the works for awhile now. Peach Princess needed enough time to have at least evaluated the entire NitroPlus product line to see which games were a) available for localization (not all titles a company ever put out are actually releaseable; older titles may have had some resources become lost), and b) were titles PP wanted to sign up on.
Then they picked the two initial games for translation. I presume that work began on them some time ago. PP has been hinting for months at big things in store for AX, I doubt very much any deals were signed the day before. So the titles are probably in the works, but probably not a lot has actually been done on them (PP has a full plate with the Downhill Night games).
People have been saying Kazoku Keikaku was announced about 2 years ago; this seems right to me (my recollection is a bit hazy). Here it is going gold master. I guess, the only other real sources of info we have right now, are Japanese proficient people: How long is Family Project, compared to the games just announced? If Nitro+ games are really long, I’d expect it to take awhile.