At this point, anyone who really cares about getting speedy Android updates knows to avoid using Verizon if possible, with a few exceptions for flagship devices. Those exceptions don't extend to tablets, even high-end ones. Case in point: the Verizon Sony Xperia Tablet Z2 is now getting its Android 5.1.1 update... a year after the software was released, and more than four months after the release of the latest version, Android 6.0. Such is life.
The tablet is coming from 5.0.2, and according to the release notes on Verizon's support page, it doesn't add anything except the changes in AOSP and the latest security patches. The page makes no mention of size, but these updates tend to come in at around 600-800 megabytes. They also tend to come in batches, so if you happen to be one of the people who spent five hundred bucks on the Verizon edition of the Tablet Z2, you may have to wait another week or so before it actually comes in.
If you're waiting for a Marshmallow upgrade, you'll be waiting for a while. Based on the timeline of this update, the next one probably won't be ready until late this year... if it comes at all. The Xperia Tablet Z2 was first released on Verizon back in July of 2014, so any further updates are basically theoretical at this point.