Personally, I have no problem with the idea of 2 items per type with 4 flex slots.
The thing is, we'll have to have something else to spend souls on if they reduced the total number of items you can have. I strongly suspect we'll get one or more of the following (given that the total number of item slots is reduced)
1.) You can spend Souls to upgrade an item in a give slot to another tier. This might increase the effectiveness of a given passive, but it will certainly increase the value of any stats on the item at a minimum.
2.) You'll be able to spend souls on enhancing one or more of your abilities directly. This would basically be the "blue" items being discussed here, but wouldn't show up as items. Most likely, it'd show up as an enhancement directly on the ability.
3.) You can spend souls to directly enhance a given category, granting things like baseline resist, Weapon damage, Spirit power, etc.
4.) Soul values will be cut dramatically.
In any case, they can't just cut the total available economic space without also doing something drastic with the rest of the soul economy. That's why this will be the first major update we've seen in a while, it's a total revamp of soul economy.