From all I've heard the black levels will be a slight downgrade. I'm in a similar boat and I am wanting to replace my Rs45 with either the Sony HW50, VW95, or the RS46.
I had an RS2 just last year and I can tell you that the RS45 has better motion, is brighter, and has a sharper pic. The Epson is likely going to surpass the RS2 in these areas as well. The black levels on the RS45 are about the same as the RS2 if you clamp the manual iris down all the way with the exception being the RS45 has bright corners. Even with the iris clamped down though the pic is still brighter than the RS2. Personally I was very happy with this move. The biggest question with the change to the Epson is how much will you lose when it comes to black levels.
Plus if you don't mind frame interpolation then this alone makes a substantial upgrade for motion (if you like this sort of look which I personally like).
FYI, if you think the RS46 might be of any interest I would get on the pre-order list. Be aware that the pre-order price in the ball park of the 5020 pricing.
Check out the shoot out thread for more details.