I guess I missed this last year…
I agree that skipping Junior year and taking it Senior year makes no sense. I’ve never heard anyone from a college, or anywhere, say they want to specifically see it Senior year. Getting to x number of years consecutively would be much easier than skipping a year.
Regarding what x is - it depends. Assuming “semi-competitive” means skipping over the top 20-30 “elite”/“selective”/whatever you want to call them, I’ve seen three years as sufficient. More might be a small benefit, but not a substantial one. Many schools only require two. I’m sure students are admitted with two, but I think the advantage of three over two is more than four over three.
If it was me, and the student didn’t have a strong interest in Latin, given the semi competitive tag (which wouldn’t include Cornell, for me), I’d stop after Latin 3.