The reason they did not do it is the outcrying against such nonsense. There is a version of the niv (rniv) perhaps that did go for gender neutral language such as plurals for singulars. I think only one textual critic prepared its text (complete tyranny). Had there not been an outcry we see what they would have done.
There has never been a translation called the RNIV. There was the NIVI which was only released in the UK. It was deemed to be controversial. But I do remember that at least one pro-ESV guy praised its translation of the book of Romans. I am not sure how different it it was/is from the TNIV.
You consider that using plurals instead of traditional singulars means it's gender-neutral? Why?
Evil speculation is what you and the other two specialize in. I deal with the actual text. Don't engage with what you think will happen. Deal with the here and now text. Otherwise y-o-u are engaging in base gossip.
As I told Y-1, you apparently are completely oblivious of the stature of the translators.
By the way
you was originally used as a plural pronoun for quite a while, before it also served as a singular pronoun for a person.