You're going to save glamour space by getting rid of so much equipment that looks the same in your dresser, or things you only wore because they were the best option for that job. I'd organize and prepare for it before 7.4.

Adding more glamour slots is tricky for them, You got to understand this isn't just a simple inventory where "number goes up", glamour is an instance (map) that is accessed exclusively through non-combat instances (because instances can't occur during combat). This game and its servers are based on instancing, every little bit they add to glamour, housing, etc, is a further strain and engineering issue. But the server end has all been upgraded, so they are working on pushing those limits.

In PLL, Yoshida explained housing item limit and debuff limit are going to take priority over glamour dresser. It will be some time before we get more slots.