Hi, it's tough isn't it? Particularly with a 4yo thrown in. We had been talking about a new baby in general terms to our BC (then not quite 4 yet) for a while, but always in the sense of 'sometime - probably not for a long time yet'. We decidedly did NOT get the nursery ready or anything. Until we were told about DD and that she would be coming home within the next few days.
Except she didn't.
It took nearly another three months (which is basically an eternity from a child's perspective). And in that time there were a couple more occasions of us thinking that it was going to be happening imminently, and then it didn't.
So when we finally did meet and then bring DD home, our BC didn't quite believe us!
So I agree that this is a 'complication' - and it is very hard to prepare a young child for the arrival of a new sibling, whilst at the same time protecting them from having to deal with the uncertainties. You know how hard YOU are finding the waiting for an uncertain duration; you probably want to spare your child that...
On the other hand I think that nothing ever really prepares a child for the reality of a new sibling. So I guess I'd advise to tone the 'preparation' right down, until you are fairly certain that a new baby is arriving within a matter of a couple of weeks or so.
Decorating the nursery could work well for that plan. As you will presumably have to remove stuff from the room, or cover things up with dust sheets. Then when you are done, just don't put everything back/don't uncover everything. Leave the room 'unfinished'. Then have that conversation with your BC that it is still 'a long time' until a baby may arrive. As PP said, point to references such as someone's summer birthday or similar, to drive home 'long'.
Then, when things are finally truly happening, you and BC can 'get the room ready' together; and it will be much more meaningful than just having a nursery ready for months on end.
The other thing I'd say, chances are you were unlucky, timing wise. Only half as many children have had placement orders in the last 6 months, as in the same time the year before. So it is not surprising that prospective adopters who were approved in that timeframe have had a wait. I know 5 months is not a long time in the big picture; but at the same time, in recent years, many people have had shorter waits. Our LA said that they matched 50% of their adopters within 3 months of approval, nearly all of the rest within the next 3 months. Not any more!
But the good news is that there has recently been clarification on that judgement which caused the number of placement orders to plummet. So chances are that more placement orders will be issued again now; plus there may be a bit of a backlog from the last 3/4 year. So I'd say there is good reason to be hopeful that you won't have to wait too much longer.
We received a LA's adoption newsletter and it seems that in that LA, they run a support group for waiting adopters - maybe your agency has something similar, to help you through this waiting game?
Good luck :)