At least being able to take a 170 this year makes this less likely. But it's really not great.
Sadly they still don't eat as much luggage as a 156 and they bring their own problems in multi with all the short platforms.
There is nothing like a 156 with the parcels van bulkhead removed, a full size luggage stack, the big overhead racks, space between the seat backs and if need be, the windowless seats by the door pockets covered over for luggage room.
Currently in vogue are humongous suitcases and on a 158 you can fit maybe 9 of them in the luggage racks if you're lucky, and you can make a pile in the bike space if you sacrifice that.
On a 156 I reckon you can fit more like 40 stacked correctly.
It gets to the point where you leave people behind because you can't fit their luggage in, rather than any shortage of space.
The extra HSTs are also sorely missed in this regard, all 3 vans in the power cars and TGS as well as the saloon stacks would be used.
The solution invariably just seems to be get on with it as best you can, though.