Gretzky should absolutely be an assist trophy and it will likely happen at some point. It is interesting to look at how the game has changed where at one point the Ross and lead goal scorer were often the same person you now can have 3 different people lead in points, goals and assists.
Renaming the trophies is a generational/era type deal. I think it has a lot to do with legend status as oppose to necessarily being the best and when a player passes on. I'm not sure now but I believe Richard was known to have cancer when the decision was made to introduce the trophy. He was the first non-politician to have a state funeral in Canada.
I'm sure Orr will eventually overtake James Norris for the title of that trophy. Norris was an owner, not a player, he didn't just own the Wings but had stakes in 2 other original six teams. He died in 52 and had a division named after him until 93. His last living son died in 1986 after selling the Wings in 1982. So a lot of time has passed. You could do it now but Orr appears in good health at 71 and there isn't an immediate rush to it. But I would actually be surprised if the trophy wasn't renamed in his honor after his passing.
The Hart Trophy would be a tougher sell. It's named after a Doctor who was the father of a Montreal Canadiens coach and been around a long time now. I sincerely doubt it would be renamed any-time soon but Gordie Howe makes the most sense.
The Vezina is never being renamed as it's in honor of a great goaltender (honored 100 greatest player in 2017) who died young because of TB.
Ross was a player and executive, and with an assist trophy named after Gretzky there'd be no need. But I could see Howe getting this.
Lady Byng seems destined to be renamed after Beliveau.
Selke seems likely but is named after an executive who won 9 rings with both the Leafs and Habs. If it were renamed you have to think Bob Gainey as he won it the first 4 years and is a Habs legend.
Smythe is untouchable like the Vezina because it's named after a long-time Leafs owner who was also a war hero serving in both world wars. IF it were renamed I have to think it'd be Patrick Roy many decades from now.
Adams is interesting with Scotty Bowman's unimaginable success (unlikely to ever be touched) but Adams is a legend in his own right winning the Cup as a player, coach and GM.
Here's a link to a 2009 discussion btw.
https://www.cbc.ca/sports/hockey/nhl-to-consider-renaming-trophies-hotstove-1.787662