The mobile Hotspot does become available when you upgrade to the DROID X, but you will pay an additional $20 on top of your unlimited data plan. The 2GB cap is for any data sent via the hotspot to other devices you connect to the Hotspot such as laptops. It does not include any data you use for surfing/downloading to your phone.
Not sure what you mean by the Update Discount. The discounted price you see on the website is the price you pay, unless you have a NE2 discount you can add.
Okay, here is how it works: Your monthly plan + $30 for unlimited handset data use. $20 additional for hotspot. Now keep in mind VZW has the right to terminate your data access if you download torrents or fileshare with your handset. Otherwise your data is pretty much truly unlimited when used from the handset.
Now the upgrade price is based on the price you are currently eligible for. If you have an existing smartphone as your accounts main line, the main line phone # should have a $100 upgrade @ the end of the 2yr contract. So if the Droid X is $299 minus $100 rebate (2yr contract price), so now $199, it will be $99 after your $100 upgrade discount.
Here is what happened when I bought my phone: I had a $100 upgrade discount, and I also waited until my contract completely ran out. They offered me an additional $50 off each smartphone handset and free overnight shipping. When it was said and done, I paid $49 for my phone and $49 for my wife's phone. I hope that helps clear things up for you.