This probably needs special handling for ports that bundle libraries purposely with no SONAME. I think the wine and openoffice ports do this.
On the other hand, is this really a pkg bug?
The fact that a .so doesn't have a SONAME is only a warning, because, hey, it may not be important.
On the other hand the fact that something uses a .so from another port without a SONAME is bad as pkg won't keep track of it.
I'm sure @bapt will say that every .so needs to have a SONAME :-)
Only the libraries in the form libbla.so.X needs a soname, otherwise when linked to a binary, the binary will be linked to libbla.so and not the libbla.so.X it should be looking for.
The check should not happen for ports that have the BUNDLE_LIBS=yes knob