Not sure it really matters, does it?
Neither title is used for the purpose is perhaps once was. Ambrose is the longest champion in WWE US Title history, but it meant nothing because he never defended it. While the IC Title is often just an afterthought anyway.
If they did do it, I wouldn't throw away decades worth of history for the sake of creating a new title. They've already done that with the Tag and Women's titles. I'd rather just merge one into the other, probs, US into IC.