For pretty much all airlines, when the decision to cancel a route is taken there is either no detail or only very high level detail on rerouting arrangements.
Only when the dust settles (typically after a few days) does the reality of the rebooking situation fall into place when the managers have put the reticketing agreements in place and operational teams who have to do the rebooking know what is really permitted.

So, DON'T PANIC yet.... there's is plenty of time - for most of us its several months away, albeit some of of have travel over the Christmas period when rebooking might be harder due to availbility.

And if and when the dust has settled the proposed new itenary (which by default is likely to be LHR-AMS-CGK-wherever) doesn't work for you, work out why it can't work [hint: I can't leave that early/late.... I arrive too early/late] and then clamly ask for other solutions, and if you can do your homework for what you would like instead with dates and flight numbers that will be useful. If you're on the phone the proposed option is not going to work, ask for the booking to remain unchanged and hang up, as you will usually only have one opportunity to modify your reservation.