I wonder if we'll see a card pop up with 48GB of GDDR6X when they start making those modules.
As for if a RTX 3090 is or isn't the new titan it doesn't have the name or 100% of the core count, though it is the top GPU short of Quadro/Tesla right now, so it could be either way, depending on what you consider the key aspect of what makes a titan a titan.
I'm trying to focus on price and performance mostly, and less so on if it has maximum cores or not, though I know it's important to some. (Titans have been out of my price range from the start, so that likely influenced me to ignore maxed out core count)