u/FoundationSafe1255

First thing first I am not saying there should be a fourth installment. 
Each part of the trilogy shares a few minutes with the one(s) next to them, the ending of Part 1 and the beginning of the second are the same thing. 
A new one probably couldn’t do that, with that in mind it would work most probably best as different from the trilogy rather than expanding it. 

I think the moniker Part 4 could work but only if it was directly following Part 3. However most discussion about that were made far later than the latter part.