Guild Wars 2

Having no interest in Hot, if I purchase the main core game from one of your 3rd party providers, will I be able to install and play the main core game?

Yes, but the only real reason is to get it from a 3rd party, is to get it at discount, if it is the same price, there would be no reason not to. Plus 3rd party have their own policies on refunds, you cannot ask Anet for a refund if you buy 3rd party.

The core version will no longer be available beyond the currently accessible keys, and will be bundles with HoT from here on out.

Yes, but you will not have access to certain (future) features and specialities. You will be able to play the game as it is now. (including the update releasing tomorrow)

Go to amazon and get it.