This would be terrible news. Not because it is Topps/Fanatics, it would be equally terrible if it was just Panini.
Competition is what keeps companies honest and forces a good product. We need more companies not less. Even as it is now, Topps and Panini can afford to churn out sub-standard collections because there is no competition to what they are releasing. Panini can throw out poor FIFA 365 collections with half as many limited editions as there are cards in the collection because there is no competitor to that collection. Topps can do the same with some of their collections because Panini cannot even try to touch the collections for a number of years. Even when a license is held, the first collection is usually a sign of intent (Euro 2024 being a BIG anomaly) and then collections tend to be meh until the license is near renewal when all of a sudden it matters again. I don't know much about the US market and NFL/NBA etc which I don't follow.
It is hilarious that in the article it says "Panini America sued Fanatics in 2023 for antitrust violations, alleging the company has created a monopoly in the industry." but they are considering a sale, which could only realistically be to Fanatics, which would create an even larger one. They have clearly valued their company more than their own revenue to generate a higher price, even if it is counter intuitive to their own lawsuit.
I think this sale will end up happening and it will be awful for everyone except shareholders at Fanatics. Quality absolutely would decline when there is no alternative, we see that in every industry on Earth and this will be no exception.