I do understand that vosotr@s is not used in most, if not all of Latin American Spanish-speaking countries, but suppose a Mexican or a Peruvian goes to Spain to see his distant relatives (who use the peninsular variety of Spanish), will he start using vosotr@s to avoid sounding too formal?
Latin American speakers of Spanish may understand vosotros to be formal. This is because virtually their only exposure to it is through reading of the Bible. (This is similar to the way English speakers have attached a formal sense of meaning to words like thee, thou, and ye, despite those being the informal equivalent of words like tú and vosotros in the old English.)
When I first arrived in North America from Spain, speaking Castilian Spanish, I regularly used "vosotros." I soon learned not to, because most often the Mexican, Cuban, Puerto Rican, etc. speakers with whom I was speaking would understand "nosotros" in its place. It took me several weeks to adjust--maybe over a month. But it is unlikely to be the same for Latin Americans going to Spain, because they habitually use ustedes, which would not be at all confusing (just more formal).
I would guess that some would never find the need to adapt, but that most would gradually begin using "vosotros" as they became accustomed to hearing it--depending on how quickly they adapted, and on how much they interacted with the Spaniards, anywhere from a few weeks to a few months.