With the number of massive, inventory-moving sales after Infinity 3.0 launched, I am not surprised that they're not continuing with the franchise. It's a shame, because from a technical standpoint Infinity is one of the most insanely complex pieces of entertainment software out there. Just thinking about its features makes me dizzy: crossplatform, networked, user-editable, hardware accessory enabled, backward-data-compatible.
With any luck, Avalanche is in talks with a publisher about being purchased outright. That's a talent pool which would be wasted on the current type of mobile market.