You really don’t want to go down this road. I have no problem starting a movement to get Americans to call them “LEGO’s” and you won’t be able to even suggest it’s wrong because it’ll just be a contraction of “LEGO parts,” “LEGO bricks,” and “LEGO sets.” (But feel free to lambast us over punctuation and quotation marks.)
How long do you thing that they will turn the already-plural "data" into the hyper-plural "datas"? Or has this already happened, I am too afraid to check.
Data is a mass/uncountable noun now (like meat) rather than a countable noun (like coin/coins). Turning it countable involves a helper noun like data point / data points.
"Datum?" Almost nobody uses that in the vernacular.
Eh, devils advocate: when a word becomes more of a loan word than just a usage of its proper origin, doesn’t it make sense to follow the new languages patterns?
Different grammatical situation of course but similar in spirit is “latte.” It just means milk in Italian and so in Italy you’d always say cafe latte. But in the states everyone knows it as the coffee drink (Starbucks probably to blame).
Same with salsa—just means sauce in Spanish—but it’s become an English word in the states at this point and taken a different meaning.
I've seen (older) German texts where "Jesus" is declined as in Latin, eg "the apostles Jesu" (=of Jesus, genitive) or "We saw Jesum" (=accusative). Somewhat jarring. As you say - when do you stop?
LEGOs makes sense; a LEGO is an indivisible entity, of which you can have a certain number. Calling the material simply LEGO makes it sound like an undifferentiated mass, like sludge, or cheese.