This was touched upon briefly in
another thread, with valuable replies I won't reproduce here. I only wanted to raise the issue again, separately. I've been reading the excellent Collected Essays volumes, and Joshi's constant references to Lovecraft's letters make one want to find out more. Now, Ningauble, when replying in that previous thread mentioned that "Hippocampus Press has plans for a complete series of HPL's letters, in 20-25 volumes" - although I can't find anything regarding this anywhere else. This would indeed be quite a mammoth undertaking. One wonders how long such a project would take to completion.
So, my question from that old thread still stands: how feasible is it to collect all of Lovecraft's extant letters? It would be quite wonderful, should Hippocampus Press go through with this series to the end, because there are so many different volumes of letters already released by various publishes, and abridges, as has been stated.