That is the case with any new car. Wait a few more years, and he will have equity and instead of paying $4500 out of pocket, he can use that equity as a down payment and have the same results for $0 extra. I guess he may be in that situation now, which changes the equation.
You could make the same argument that he keeps it for 10 years.
I say if it's around what he is ALREADY PAYING by keeping it (by amortizing it to figure that out). It makes absolutely no difference.
Now, if the cost was like $10,000.00 then it doesn't make financial sense. But at $4500.00 I think it's a no brainer.
"Wait a few more years" as you say will now come 2 years later.
It's all the same
If he could upgrade for a $100 would it be worth it? Of course it would.
If he could upgrade for a $1000 would it be worth it? Of course it would.
What is the magic number that you would give to say it's worth it? TO HIM, not you.
I think $4500 would be a bargain. If that is the true cost and he can get the full tax credit on the new car.
People pay more per year on 1 year of leasing than that.
He better grab that deal quick. Because the dealer may not have adjusted their figures for new prices yet.