Support Upgrading OS before or after activation?

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http://androidforums.com – I am brand new to the forums, brand new to Android, and this is my first smartphone. (I had a semi-smart phone before but that's just a quick route to frustration!) My question is this: I ordered the phone and I should get it tomorrow. As you all know, it comes stock with Gingerbread and I want to update to ICS. Is is possible, or advisable, to upgrade before I activate next week when my contract ends? Would I need a Sim card to do that? I have WiFi at home. I've heard a few things about being able to use smartphones on a WiFi connection without a carrier. Is it okay to upgrade or will th (General)