I definitely would like to see a new 24 (asph) and 35 (asph). A nice add on could also be a new 60 Macro which performs well at the bellow but is also capable of high performance at infinite range. However, the old 60 is still pretty good in this respect and this might be a niche market. So more priority for the 24 and 35, please
Since the new 19 is there, I see minor importance for a new 21 for me personally. Of course others might have other preferences.
For the longer focal distances, a new 135 could also be interesting for travelling if it has less weight/form factor than the 100 APO.
Just my 2 cents
Marc