Titanforging's design goal is to keep old content relevant.
So IMO Blizzard should do this:
- disable Titanforging in the current raid tier (we have Warforging for that purpose: Titanforging works between tiers while Warforging works within a tier)
- adjust the upper Titanforging limit and range based on previous tiers' item levels.
For example: If the latest tier has normal gear with an item level of 100 then each item of a previous raid tier can titanforge up to 95 (or some other number < 100) even if its base item level would be 10 (perhaps trinkets should be excluded from this rule).