I'll let the technology for color eInk develop a bit more before I look into the upgrade. I would prefer three things:
Larger screen like 12"+. Kobo Elipsa2E is 10.3"
more vibrant colors for the color eReader. Currently, the color eReaders only have a touch of color
Better 3rd party software retailer support
Lower price. Currently: $500 - $650 for a color eReader, vs $400 for Elipsa2E
A comparison video of Color vs Black & White with Kaleido 3:
In short, for just reading the B&W is better. For color comic readers or for highlighting text in different colors, the color version is better. I prefer less distractions and the better reading experience.
"Where is boasting then? It is excluded. By what law? Of works? No, but by the law of faith. Therefore we conclude that a man is justified by faith apart from the deeds of the law." Romans 3:27-28