As it was a previous kalpa, does the World-River have a counterpart in Nirn's current kalpa?
It's not Time. The "World River" is a metaphor for the flow of existence (Linear Time in conjunction to Space) in each Kalpa, and it's not really a 'thing', rather a force within each Kalpa.
Here's what I think might fit. It is a promise of something new.
"'The magical cross is an integration of the worth of mortals at the expense of their spirits. Surround it with the triangle and you begin to see the Triune house. It becomes divided into corners, which are ruled by our brethren, the Four Corners: BAL DAGON MALAC SHEOG. Rotate the triangle and you pierce the heart of the Beginning Place, the foul lie, the testament of the irrefutable-for-a-span. Above them all is the horizon where only one stands, though no one stands there yet. It is proof of the new. It is the promise of the wise. Unfold the whole and what you have is a star, which is not my domain, but not entirely outside my judgment. The grand design takes flight; it is transformed not only into a star but a hornet. The center cannot hold. It becomes devoid of lines and points. It becomes devoid of anything and so becomes a receptacle. This is its usefulness at the end. This is its promise."
- Sermon 13
This is just a Vehk-Esque explantion of how eveything eventualy becomes Grey, changing a Grey Maybe, to a Grey Nothing (The begining and the End,
O), until it is split again by AE to form the next Kalpa.