As I have read blogs and news on Quattro, they are trying to release it before summer. But another guy, who went to CP+, was also told from one the Sigma staff that it could be before "Golden Week," which supposed to be meant the end of April to beginning of May.
So, from May to July, maybe?
About the price, I only saw one source (sorry I don't have a link) guessing around $800.
Many Japanese are also hoping and guessing to be around this price. But no guarantee of course.
I though I was going to buy DP2M, but as I have been researching on both M and Q, I am so tempted to go for Q.