Yeah it's very annoying. The problem is Verizon's testing procedures (or so I've been told) are VERY strict. Add to the fact that the Xoom isn't a priority device for VZW anymore, and yeah...we continue to wait. The WiFi-only Xoom has had ICS since December, and (again, so I've heard), Google had the ICS ROM for the 3G/4G Xoom ready not long after that. To add further insult to injury, Google and VZW pushed out an update to the 4G Xoom in February that was just a Honeycomb update (3.2.6) to fix data connectivity coming out of airplane mode. Annoying.
With the Galaxy Nexus, at least two 4.0.4 builds have been pushed to devices as part of a soak test (IMM30B and IMM76K), but neither made the cut apparently. But since they went out over the air, we have the files and can run those if we want to. With the Xoom, there hasn't even been so much as a soak test, that we're aware of anyway.
Samsung Galaxy Nexus (SCH-I515/Verizon) :: mysid 4.2.2/JDQ39 :: Radio I515.FK01 (CDMA) / I515.FK02 (LTE) :: Bootloader PRIMELC03
Motorola Xoom (MZ602/Verizon) :: trygon 4.0.4/IMM76L :: Radio 03.1A.65P (CDMA) / 07.1F.00 (LTE) :: Bootloader 1050
LG Nexus 4 (LGE960/AT&T) :: occam 4.2.2/JDQ39 :: Radio 2.0.1700.48 :: Bootloader MAKOZ10O
Asus Nexus 7 (ME370T) :: nakasi 4.2.2/JDQ39 :: Bootloader 4.18
Samsung Nexus 10 (GT-P8110) :: mantaray 4.2.2/JDQ39 :: Bootloader MANTALJ12
OTAs and factory images, past and present, for every Nexus and "Google Experience" device since the HTC Magic at http://www.randomphantasmagoria.com/firmware