Future

Generally people say "In THE future." I've never seen in 'a' future, though I'd suspect some people say it because they believe that time diverges á la Back to the Future 2.

You only say "in futures" if you work in futures trading.

You can say either "in future" or "in the future". The tendency is to use "in future" to refer to relatively limited actions -- "In future, please address all such correspondence to our customer service department" -- and "in the future" to refer to broader situations: "In the future, all cars will run on a mixture of vodka and cider vinegar."

The phrase "in a future" could be used when discussing multiple possibilities for the future.

"In a future without cars, the air would be much cleaner."

This future may never come to pass, so it is spoken of as one of many possible futures.

For most practical purposes, there is only one future. Therefore, "in the future" is the correct formulation.

On Star Trek (or perhaps if you are a physicist), people are sometimes aware of more than one future. In this case, "a future" makes sense, although it may still sound a little weird. We're still talking about the same kind of future here, it's just that we're allowing that there may be more than one. This doesn't make sense for everyday usage.

"Futures" as traded on stock markets, are an diferent beast altogether. They are objects whose name is derived from the fact that they are a bet on the future value of some commodity. I don't think it's particularly useful as an example here.

Finally, I believe "in future" is simply a contraction of "in the future" used to reduce the length of a telegram or memo. I don't think it's any more grammatically correct than any other telegram-speak. Just my opn stop Hope topic clrfd smwht stop

Futures can be used in the plural form when speaking about the different futures of more than one object.

"John's future is bleak."
"Shirley's future is bleak."
"John and Shirley's futures are bleak."

If John and Shirley are separate from each other in the future, then their futures will be different. If they will be together in the future (obviously I mean distant future) then future would be in the singular form.

"John and Shirley's future is bleak."

Does that make sense to others?

However, I don't think you'll ever say "In futures, we'll have..." because you are saying "we" will have the same ... in the future.

"In future" is chiefly British usage. In the US we almost universally say "in the future" in cases when Brits would say "in future".

I can think of another occasion when one would say "a future".

A boyfriend is trying to break up with a girlfriend, and say to her "we won't have a future" or "I won't see us having a future".

In this case "a future" is one of many possible futures there can be.

As to when you would use the plural form "futures", see the sentence immediately above this one, although I am not sure if its use is grammatically correct.