When future Bitcoin is sent to an address that existed BEFORE the fork what happens?
Do old addresses not have an assigned chain or do they divide or what?
I really don't know the answer here. I am expecting many payments in the coming days and weeks some of which have staked, aged addresses. Hmmm. A little insight would be awesome. Thanks !
If you want to get technical, it depends on the
type of fork. A conventional softfork would almost always result in one single chain, so that one is kind of a non-issue. The SegWit softfork we're going through in the very near future, assuming all goes smoothly, won't result in you having to worry about which chain you're on, or which address you're using. It should be a near-seamless transition and you probably won't even notice any difference. Everything will carry on like normal. If or when people eventually opt to use the new format SegWit addresses, they can still send payments to you even if you aren't using the new format.
A "user activated softfork" is a little more confusing, because those
can potentially cause, or otherwise result in, a hardfork and a permanent contentious split if the desired outcome isn't reached (in which case see the next paragraph). But note that we have hopefully avoided such an event now.
In the event of a hardfork, any addresses generated before the fork can still be used on either chain. You would have the same balance on both chains to begin with. Providing there is adequate replay protection, after the fork occurs, transactions
should (in theory at least) only appear on one of the two chains. So if you want to receive a payment, you would have to make sure the person sending you the payment is doing so on your preferred chain. But again they can still send payments to any current address you're already using now if you wanted them to.
To sum up, in just about any fork scenario you can envision, you can still use your current addresses. You just have to be slightly more careful with hardforks to make sure that you're getting paid on the chain you want to be paid on. Plus, as others have pointed out, it's usually best to wait for a few extra confirmations just to be on the safe side.