We're also hearing that 4G will be a $10-20 plan add-on, a price that would almost certainly include access to the EVO's 8-device WiFi hotspot capability. We're definitely buying that 4G won't be included with the base Simply Everything plans since we encountered an EVO at CTIA that hadn't had WiMAX access "enabled" on its account even though EV-DO worked just fine; the services are being treated separately. Verizon's recent announcement about free hotspot access on its Palms certainly puts some price pressure on Sprint here, but charging a premium specifically for 4G probably isn't an issue as long as they're clearly able to demonstrate its speed advantages in the markets that have it live.
Update: We've been written by several folks insisting that the add-on fee will be for the 4G hotspot service alone, not 4G access from the EVO itself. Let's hope. Thanks, everyone!