It's an interesting question.
I suspect the role of scrolls will depend on the importance of consumables to the Inscription profession. Many people were expecting glyphs to be like enchants, but they feel more like potions. So Inscription may already have a viable consumable.
However, scrolls could equally become the mainstay of Inscriber's day-to-day activity: If every member of a raid was required to "scroll-up", a lot of scrolls would be needed. But last year's alchemy changes moved away from requiring many different potions, and requiring scrolls would place new stress on the raid community.
What we do not yet know is how glyphs scale over time: How they get better with successive patches. Most of the manufacturing professions gain new, improved recipes over time. But how exactly do you scale a Glyph of Shred? 1.1 additional targets? Tricky.
So perhaps Inscription is not going to evolve at all, just as the gathering professions don't change dramatically? There might just be a few new glyphs to support the new spells in each expansion.
The long-term role of Inscription isn't at all clear yet. I think it may yet surprise us all...