It was probably in ITN's favour than the brand change to ITV News happened when it did - the removal of News at Ten, the further edging towards sensationalism and 'light' politics, the disastrous News at When? era, style over substance etc etc are all associated with ITV rather than ITN. If the name change hadn't happened, people on here would have the same usual complaints but it would be ITN accused of dumbing-down, being a shadow of its former self, and so on, and saying that maybe a change to 'ITV News' might give them some real presence and authority!
I can't see ITN being reinstated on-screen under any circumstances (they even removed the logo from the endcap), and would it make any sense either. But we've been over this time and time again on TVF.
At that point the ITN brand hadn't been gone for long - it's often forgotten now that it wasn't completely removed from ITV News bulletins until 2001 (rather than March 1999 as is often supposed). I think at this stage the name has been gone so long that it would be pointless to revert back.
If (and they probably will eventually) ITV do acquire 100% of ITN I suspect they would rename the company ITV News Limited rather than revert ITV News to ITN.
...which then raises the issue of whether Channel 4 and Channel 5 would really want their news output to be seen as being produced by ITV News.