Considering the entire internal frame of the 15 and 16 Pro (and Max) stayed as aluminum, and the titanium was never more than a very thin strip around the outside, I don't know that it will make much of a weight difference. Most estimates I've seen put the total weight of titanium, in the Pro model, at about 10g-12g. Aluminum is ~60% of the weight of titanium, so you looking at about 7g of weight savings.
I want a lighter phone, however they see fit. I never liked the weight of my 13 Pro, and I similarly dislike the weight of my 16 Pro.