These are some thoughts on "Going to" and "Will" : Are they expressions of a promise or merely an indefinite intention?

I am not sure, but maybe L1 transference could account for this phenomenon (common error), unless it is different in British English, although the site that one English teacher quoted previously, http://www.ego4u.com/en/cram-up/grammar/future-mix , prescribes will and going to as stating something that one cannot change (weather, it will rain) and stating a planned activity (decision) respectively with no mention of uncertainty.

Examples would be:
It is going to rain tomorrow. (conclusion with regard to the future)
It will rain tomorrow. (assumption with regard to the future)

In Portuguese, the future indicative of the verb for "to be" (ser) is será, i.e., "He will be, It will be."

But Será is also used in the sense of a polite request such as "Would you close the window," which translates as "Será que você poderia fechar a janela."

Será que você poderia sentar na outra cadeira?

“Is it possible that you could sit in another chair?" The last example is from the article, Differences and Similarities in. Men's and Women's Directives in Carioca Brazilian Portuguese.

http://www.jstor.org/pss/341699 is the link to the beginning of the article.

Será is also used to express uncertainty:" Is it possible that I am pregnant," or "Could I be pregnant?" would translate as 'Será que estou gravida?"

So, it is my hypothesis that this built in connotation of será (will be) in latin languages could influence the feeling of English learners that Will "should" express uncertainty, as it does in the latin languages.

I asked my Portuguese teacher, a retired professor of linguistics, what he thought about my hypothesis and he could not verify it, but thought it worth investigating.

I would be interested to hear from speakers and or teachers of British English, Austrailian English, Canadian English, Indian English, African English etc. where English is one of the official language of the country whether going to and will are used interchangeably (synonymously) or whether there is an element of uncertainty, as is claimed by one textbook that I have personally seen in use in Brazil.

If the other Englishes besides American English are different then there is no problem with teaching will or going to as merely intentional (a possibility that is not definite). However, if the other Englishes also conform to the usage that I grew up with, that will and going to express a commitment (promise, definite plan) then maybe the writers of English grammars that teach them as expressions of uncertainty should be alerted.