I don't think anyone has to worry about a map reset anytime soon. I can't confirm this as we have no idea what 1.8 and bukkit is going to be like yet. But as I've said many of times my best guess is when 1.8 comes around we will have a 1.8 map as the default map, then the current map will be called the old map where it will be accessible via portals. Much the same as how multiworld works on our server now (creative world etc).
Items will be staying also with them most likely being transferable between worlds, unless there are some limitations. I'm also guessing that the 1.8 world with have more of a chance of getting reset for 1.9 or other updates as players will demand the latest build, again I don't think anyone has any ideas about this yet as we have no idea what 1.9 will bring.