IMHO, it's a gimmick that will go away entirely. And convection isn't even close to being "standard". Most ranges and ovens sold are not convection models.

I'm not saying that the convection models sell in the larger numbers, but looking at the wall oven models on AJM, there are 250 convection models and only 95 non-convection. The percentage is even higher when considering only single ovens.

Convection is a fairly cheap feature, even when done right. Steam, depending on what is being implemented, is not.

Steam combi ovens will not proliferate, but they will not go away either. Their cost is beyond the interest or budget of most people, and most of what they do can be done in another manner: if all you want to do is put a crust on some bread, you
can put a pan with some lava rock on a lower rack in a regular oven, and pour some water in at the appropriate time; you can steam on the cook top, etc.

I don't think that steam combi's will become as common as convection - to make a combi you need to add a water boiler, much more intensive controls ( so you can set the amount of steam ) make the oven cavity more or less sealed ( so the steam doesn't escape ) and stainless so that it doesn't rust, and make the glass not shatter when it gets hits with condensation. On the other hand, Sharp has addressed all those issues in a countertop version 120 volt model for under $500 - I would think a regular manufacturer could make a combi steam wall oven at 240 volts at a price much more attractive than the current offerings from the high end manufacturers which are admittedly very expensive.