There's actually a fairly short list of things that would make
Inkscape ideal for graphic design. 
 
If graphic designers are our primary audience, then we need to look very seriously at closing that gap, and beyond at how we can make Inkscape better than alternatives in terms of usability, features, and performance.

Product design, on the other hand will
pull it into territory that is better left for 3D modeling and CAD
programs. There are already specialist FLOSS programs for this, also
vector based (Blender, FreeCAD, etc.). From this perspective, graphic
design is the only choice with enough general overlapping
functionality to make it useful for the broadest range of applications
related to what Inkscape does best - 2D vector graphics.

Makes sense to me. I'm not sure how many people are using the tool this way.
 
The reason designers are entrenched in the Adobe "ecosystem" is that's
what is taught in university, and when they look for alternatives,
there aren't any programs that fit the bill entirely for vector
graphics. They are looking to replace Illustrator, the functionality
of which isn't covered by any other FLOSS project. In fact, Inkscape
is key to making pro graphic design possible on Linux. Adobe isn't
even an option on Linux. So a decision to move away from graphic
design would be a quite terrible loss for all manner FLOSS artists.

I agree. And just to clarify, I'm not advocating abandoning anyone, I am just hoping to identify a market who could be persuaded to use Inkscape on its own merits now (or in the near future), and not strictly because it is the only vector drawing tool available on Linux or that it's free of charge.
 
That's true, if tools (in Inkscape) are built to utilise the svg spec
to produce pain-free vector animations (for example), or style sheets
that integrate easily with web content, all those things will be
beneficial to designers of all types. Producing software that takes
the complexity out of it is good for both techies, and non techies
alike.

Yes, yes, yes!
 
Mac support is something to work on, but the fact remains, there
really are not any other good options for vector illustration on
Linux. I think a FLOSS focused vector program should fill the gap in
tools for FLOSS operating systems as a primary goal, regardless of
what other more popular OSes are out there.

It's a worthy goal, and I would sure appreciate it because I use desktop Linux. :) From a marketing standpoint, however, I'm not sure we're going to find new interest and greater adoption from the few of us on Linux, since we really don't have any choice anyway. Let's not abandon Linux users, but we must also acknowledge that statistically speaking almost everyone else is different than us in this regard. Once they're using Inkscape, maybe there will not be as much keeping those graphic designers back from using Linux also.
 
We gain no ground by being
afraid to go up against Adobe's Creative Suite.

Believe me, I'd love to take them on. We can't ignore their dominance in the graphic design market however. The only way to beat a giant like Adobe is to use their strength against them. They have an entrenched user-base, who will keep them back from trying new and innovative things, especially in regards to workflows and interface design, because people don't generally like to change the way they do things. This makes them slow. They are also trying to be a tool for as many people as possible. This makes their software complex. And lastly they have broad adoption in the market and have more to lose than to gain by trying new things. This makes them risk averse. To beat them we cannot be these same things.
 
I submit that the path of least resistance is not necessarily the path
to success. Making Inkscape for a niche group of readily accepting
users will keep Inkscape a niche program used by a small segment of
the population, and it will leave a large segment of designers who
want to use free software waiting for something else to replace
Inkscape as their vector editor. Right now, nothing else comes close.

I totally agree. And thank your for engaging in this conversation. It helps a lot!