Originally Posted by
bigevil
If it's a total waste and moot, then I'll just wait a few months and go for a dedicated road bike when I've saved some more $, but I thought it might be the perfect middle ground since I could eventually throw these on a road bike purchase and also see if I can some performance benefits in meantime!
It would not be, in any way, shape or form, a total waste.
What I would do is consider where you think you might want to be down the line -
If you're the kind of person that's going to be all "Di2 or nothing!!!" with regard to a road bike... then maybe you keep the money in-pocket to get you there sooner, because bikes trimmed in Di2 tend to have pretty nice wheels.
On the other hand, if you would be perfectly happy with mechanical Ultegra or 105, I would pop for the wheels now. You'll get the benefit of having and enjoying them immediately, and most mechanical Ultegra bikes (and all 105 bikes, that I'm aware of) have place-keeper wheels, anyway. Basically, you'd be looking ~$1300 for the wheels and $2500+ for the bike (you can find some really nice Ultegra bikes, with place-keeper wheels, in the $3-3.5k range).
And, if nothing else, these wide rims, particularly the hookless ones, would be awesome to keep on a dedicated gravel rig.