Waiting for Windows Phone on Sprint& Verizon does it make sense to use the buyback program bestbuy has, since Mango update will bring the second wave of Window Phones? I understand that as an early adopter it sucks for 2 year contracts to find out later in the year your carrier launches the slab device you wanted but needed to upgrade due to

4.1.11 Sprint I have an upgrade due-$150 March but will lose it , or phone dying etc.) I don't want the HTC Pro 7, but if I can use it and then sell it back to get a better device when Mango comes out is it a bad choice? I am trying to work it out in my mind how it hurts, how I break even, or ahead. What are your thoughts or experiences? I am open to different ideas, either way my bill will go up with Sprint $10 or any other carrier...
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Sanyo SCP-4900, Sanyo MM-8300, Audiovox PPC 6700, HTC Mogul PPC-6800, HTC Touch Pro 2, HTC EVO, Samsung Focus, HTC HD7, HTC Arrive.