They are going to a new processor core?
I believe this is called "extending the product line."
I think this is a poor idea.
You are welcome to think that. However, it seems very unlikely the current Arduino lines would be discontinued. The team is expanding the capabilities. How is that a "poor idea"? Unless you want to suggest the team sitting around waiting for others to have better idea in this area. (That way they emulate large corporations and not open source projects. If that's what you want, then I agree on "poor idea.")
There is going to be compatibility issues, major changes including a different compiler and no eeprom can be a big deal.
Very few projects make use of EEPROM. As for the others, if someone (not you) would stop complaining about the changes made with the 1.0 release long enough think about why, they might see the changes lend themselves to a new processor core.
Also there is no significant benefit over an atmega 2560
4 times the RAM, significantly faster core speed, and a 32-bit instruction set. Yeah, I don't see anything better there. Well except for everything.
The only differences I see are higher clock speed (unnecessary in most cases), no eeprom and alot more SRAM which does not make too much difference once you have 8K or more.
So you went from "no significant benefit" to " alot more SRAM". Well, maybe that's the significant benefit?
For people saying the "Arduino isn't enough", the Due comes in. For those who believe it is, boards like the Uno will continue to exist. If nothing new was released, there'd be a large number of "why doesn't the Arduino team do something ARM??!?!?" threads.
Regardless, nobody is every happy with any direction the Arduino team takes.