Will I get a new iPhone with my warranty?

I have a iPhone 4s that just broke literally a few hours ago; more specifically the lock button dosent work, it's basically stuck and won't work so my warranty should cover it but I got the phone at bestbuy so I'm wondering if I stall a little longer maybe a few more days if they would just give me a iPhone 5? I don't know; I've had things like that happen to me in the past with phones where they just give me a upgrade instead of giving me a the same phone so I'm just curious.

No, you will get a referbished iphone 4s as long as it was never jailbroke… Not a 5 no matter how long u wait.

They are not going to give you an iphone 5 just because your 4S is broken.
some lucky ones get a new generation of the phone when their phone is broken within the warranty. But this is because apple does not keep old stock. They would not restock old generations if they have a new one released. Because iphone 5 is not even out on the market yet as of today, and they probably still have a lot of 4S in stock, even if they give you a new phone you will still get a 4S for now.
I have an iphone 4, and even though the 4S came out very soon after the 4, I still got an iphone 4 from apple when mine was broken in March 2012, (4S was out a long time in the market at the time).so don't give too much hope into getting a 5. You never know though, you might be one of the lucky ones.

No, they will not give you the iphone 5 just because your 4S is broken,
but the lock button is not a big deal and you should be able to make a reservation at the genius bar
and they will give you a refurbished 4S. It will look like a new one so don't worry
but make sure to back up everything on your old 4S