I have a novel where X-Men and Star Trek crossover called Planet X, so there are stranger crossovers then D&D and MtG.
I seriously and utterly doubt anything from MtG will be in BG3. Like, -100% chance outside of MAYBE a nod or easter egg. For their first chance at something this big and the first return to an iconic series in such a long time, it'd be hard to imagine they would ever choose something far off DnD before adding something else from DnD. The Magic the Gathering crossover stuff has been very divisive in the MtG community and already plans off the wildly multiversal nature of MtG (like, even more extreme than DnD) where basically every span of sets is a new world and history and planeswalkers walk planes, so they just hand-waved adding in known IPs.
Like, Warhammer 40k...
So no, I wouldn't take it seriously. It's obvious the only reason WoTC is doing this is to milk $$$$$$$$$.
However, you're not wrong. There are some weird canonic crossovers in existence, such as Sonic the Hedgehog and Megaman...
