There were several articles related to this subject in the Summer 2006 issue of "The Craigendarroch News" (I'm an owner there).
First, the cover article titled "Hilton comes together after 40 years" starts out with "The Hilton brand was reunited across the globe, when US based Hilton Hotels Corporation (HHC) purchased UK based Hilton Group PLC earlier this year." It goes on to say that HIGVC owners should see no difference in day-to-day operations, but "where we will benefit is by our much closer association with Hilton Grand Vacations Club."
In a sidebar, HIGVC owners at Craigendarroch (and presumably others) are now being offered membership in HGVC for GBP245. If they're being offered membership in HGVC, I'd have to guess that eventually HGVC members will be offered membership in HIGVC. In the best case, perhaps the two organizations will simply merge! (my speculation only).
There's a back page article about Hilton Vilamoura Vacation Club, whose lead sentence starts "Hilton Grand Vacations first resort on mainland Europe will open next year....". Note they don't say HIGVC, they say Hilton Grand Vacations. I assume the author misspoke and means it belongs to HIGVC, but we can always hope.