When pulseview is given the -i command line option, specifying the input file 
to load, it's assumed that the file is in srzip format. Other formats strictly 
require the user to specify -I as well.  A similar constraint applies to 
interactive use of the GUI, where it's essential that the user chooses either 
"Open" or "Open As", depending on the file type.

sigrok-cli uses a method where in the absence of -I format specs the list of 
input modules is queried which of them can handle the file format in question. 
Pulseview should use that method as well.

Of course that auto detection only takes effect for those input modules which 
support it, and when the format reliably can get detected (some can't, due to 
ambiguity between several supported formats). This means that support for -I 
needs to remain, it's just that -I could get omitted when there is no doubt 
about the format of a file.