Actually, you can even run latex --output-format=pdf foo
Well, to get something useful, you have to make sure that the latex format is created with useful setting for e.g. \pdfhorigin and \pdfvorigin.
If you just latex -ini latex.ltx latex --output-format=pdf sample2e you'll get a messed-up sample2e.pdf.
This means, that we either have to make sure to set useful defaults for *all* formats that we dump with pdfetex or that we reactivate the config file.
Surely those variables must be intialized with sensible values ? But when I wrote that, I meant that we probably can't expect that every package will take care of potential pdf output. So my question is : shouldn't we allow to switch pdf_output on command line only in INI mode ?
Maybe the problem is that you just don't expect from inipdfetex to be initialized to DVI output format ...
Maybe, pdf*tex should defer this message until the dvi vs. pdf decision is finally decided (don't know when this is: when typesetting the first boxes or when shipping out the first page).
That makes sense. Fabrice