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.
And a multitude was sitting around Him; and they said to Him, "Look, Your mother and Your brothers are outside seeking You." But He answered them, saying, "Who is My mother, or My brothers?" And He looked around in a circle at those who sat about Him, and said, "Here are My mother and My brothers! For whoever does the will of God is My brother and My sister and mother." Mark 33:33-35