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.
"Whosoever shall confess that Jesus is the Son of God, God dwelleth in him, and he in God. And we have known and believed the love that God hath to us. God is love; and he that dwelleth in love dwelleth in God, and God in him." John 4:16,17