Speculative guess on v4. They want to keep it quiet until released though or people stop buying v3. The 20% off on irregulars ending at the end of the month coupled with the 3rd annual anniversary of the v3 definitely justifies my speculation.

How long between original m80s and v2? Then June 2010 for v3. Is the graph a line with a constant slope? I don't have the info as I am an axiom fanboy in the making with 2 months of marinating remaining.