I think I understand your concern, but, look at the 'NEW', better, latest, greatest welding symbol example in A2.4, Figure 3 page 3.
'D', 'E', and 'S' are placeholders. 'E' stood for effective throat or weld size. 'S' stood for Depth of Bevel or size or strength. Since they are only placeholders anyway, you could use 'X', 'Y', and 'Z' if you wanted to. It really doesn't matter. These letters don't show up on a finished drawing anyway. Though they are often used in the General Notes to designate how welds are to be detailed.
My concern is confusion when trying to explain certain things to welders, fitters, or whoever.
But, Replacing 'E' with 'D' makes sense when you consider what it has come to stand for 'depth of bevel' (changed to 'groove'). And, using 'S', but in a different place as a placeholder, makes sense for 'size of weld' not just effective throat.
You still have two placeholders. They are still showing all interested parties the depth of bevel (groove) and the intended weld size. They just changed what letters are in use.
See also Annex 'D', D4.5, page 113 in A2.4.
Thus, I believe you are correct in what will happen when we see the new D1.1:2015 but there will still be two placeholders even though there will be no 'E'.
He Is In Control, Have a Great Day, Brent