When under the influence of the Cytherians in "The Nth Degree", Barclay creates a kind of wormhole to transport the Enterprise 30k light years toward the galactic core. They spend a weeks shooting the bull, return the Enterprise to Federation space with decades' worth of knowledge, but the only thing we see, the wormhole technology is never seen or heard of again.

Or is it? A couple years later scientists make a breakthrough in developing soliton waves, another form of "warp without warp drive." Clearly, they're not the same technology. The soliton wave carries its payload at light speed through normal space, while Barclay's wormhole is a subspace phenomenon. (If anything, it most closely resembles the quantum slipstream drive from Voyager, though that's arguably a transwarp phenomenon, I think.)

Regardless, the timing is curious! Is there any reason to think, or doubt, that the Cytherians and their wormhole represented a missing piece of the puzzle of creating a soliton wave and using it for propulsion?