<tinfoil hat mode ON>
Maybe they started to sell Xmegas under the old brands to slowly migrate everybody onto Xmegas
Truth be told, at least on paper, these new models appear to be superior chips. More peripherals, one pin programming interface realized with UART, memory-mapped flash, the event system...
And they even tend to be cheaper, like the 8-pin ATtiny212 which beats the old ATtiny13A on price and specs.
One obvious disadvantage is more registers which means few useful ones are accessible in 1 clock cycle anymore.
I feel that they are hoping to avoid scaring customers with a new name, although these new chips are really a new family and should be treated as such.
Relative to the older ATMEGAS, they are definitely superior. Lot's of welcome improvements, but sadly at the cost of having to refactor code after going through the initial learning curve that was not immediately obvious. I should have looked closer for sure while I was initially choosing these, but in the end, I think the new features will outweigh the code updates.
The price is definitely nice on these. My first project is fairly priced sensitive so that is a bonus, but really I chose it for the apparent improvements in real-time control I am expecting with the control independent peripherals [CIP]. That feature will offload some pressure for me to have super-tight code to accomplish time-sensitive tasks.
Anyway....guessing I will spend the next couple of days becoming friends with these little chips. I need solid I2C, ADC, and UART modules right off the bat. Everything else can be learned as needed. Surprised how little information there is after a year on the market. I was quite spoiled with the massive resources for developing the older ATMEGA AVR's. It was so easy to find discussions and examples for just about anything.