The Samsung-sourced femtocell that Sprint and Verizon have been offering (as the Airave and Wireless Network Extender, respectively) is all well and good, but it's got one fatal flaw: unlike AT&T's aptly-named 3G MicroCell, it doesn't have support for 3G data -- it's compatible with CDMA 1x alone. Verizon's fixing that later this year with an updated model from Samsung, but thanks to a fresh FCC filing, it looks like Sprint will be taking a different route by roping in Airvana for the Airave's successor. On top of EV-DO, the interesting bit about this puppy is that it supports a VoIP-routed landline connection around back; we're not sure whether Sprint actually plans on enabling this extra jack, but it's specifically mentioned in the draft manual, so we wouldn't doubt it. No word on a release just yet -- but FCC approval is frequently one of the last steps on a product's road to retail, so we might see it soon.