Up Front fan, Cats were once worshipped as gods and they haven't forgotten this, Combat Commander series fan, The Raven King (game publisher) ... that's me!, Fields of Fire fan
Slywester Janik, awarded the Krzyż Walecznych (Polish Cross of Valour), August 1944
Will I be able to purchase the expansions and new nationalities and play them with my current copy of Up Front?
You'll have to get used to reading your RR stuff backwards on the old cards, as 0 is now close combat range and 5 is as far away as you can get, and the new soldiers will have weapons detached, but otherwise, it shouldn't be a problem. The fundamental mechanics and rules aren't changing.