Will iPad work with Sprint wireless broadband usb modem?
The iPod demonstrated on the 27th does not have an onboard USB host port, so there would be nowhere to plug it in.
If you use a dock, there's a USB port. But the only use that has been announced for that port is basically to act as a PictBridge master for pulling photos off digital cameras. There's no evidence (yet) that there's any software framework in the OS to allow it to be used as a general purpose USB host.
Maybe,
maybe, Sprint might write an App for it and it can work through a Dock Connector adaptor like other officially supported 3rd party accessories. But in order for it to be useful, it would have to be an App that actively multitasks in the background (and there's no official support for that) so that you can leave the Sprint connectivity App running while you switch over to the Internet-connected App you're actually interested in using.