Hi,
Well, I guess the answer is that he is weaning - a process that begins when a baby has something to eat other than breastmilk - but as to when he will have his final breastfeed, that's something we just don't know.
For as long as your son feeds, there will be milk there to meet his needs. Many children spend a long time just having one or two feeds per day - and that's completely normal. Some mothers worry that their baby would need to feed more often or that their milk would "just dry up" - that's not the case. Many mothers find that a new pregnancy at this stage speads up weaning. Might that be a possibility in your case.
You've breastfed well and long - good on you. It might finish sooner ...or later, but for now, just enjoy it.