Update: The Sanyo 5500/VM4500 also appears to be getting an update for the same reason, Sprint is currently testing firmware version 1.009SP.
Sprint is currently testing firmware updates for both the Sanyo 7200 and 5400. Early reports indicate that these updates (1.034SP for the 5400 & 2.047SP for the 7200) are being prepared to improve ReadyLink services.
These updates do not add SMS (a feature Sprint originally said would be available on the 7200 and 5400). Of course, there is also no guarantee that these updates will ever be released, but it is more likely than not that they will.
