I wouldn't bet VM out of the upgrades just yet. Read my thread here:
Vm sent me a text about upgraded 3G - Android Forums
I'm guessing LTE is about to roll out in your area. From what I've seen, things may improve but not drastically. The increase in speed would be from current Sprint users moving from 3G to LTE. Problem is, from what I've seen, most Sprint users do not yet have LTE capable phones.
The problem is, LTE phones, such as the Evo 4G, have been stuck at similar 3G speeds VM users have experienced; since there has been no LTE. Instead, many Sprint users have stuck with WiMax or other less expensive phones, rather than pay a premium for a technology that they have not been able to use.
Further, even in areas where LTE has been rolled out, LTE is not available in all neighborhoods. Many towers in these areas have not yet been upgraded to LTE. It will be several months, or even a year, before those towers are upgraded.
As more Sprint users buy upgrades to LTE phones, it will slowly improve. As more LTE towers come online, that will also improve speeds. But that may take a year, or even longer, before 3G data actually is running at 3G speeds.