Dark Heresy doesn't have to be revamped to fit into Rogue Trader, Dark Heresy characters can be used in Rogue Trader and vice versa. The main difference is the handling of money. The same with Deathwatch where the main difference is the handling of mass caualties caused by Space marine weapons and armour. If your Dark Heresy characters ever get hold of Storm Bolters and Terminator Armour, the GM will need top be using the rules from Death Watch to deal with the slaughter that will follow.
As to your other point, it could be that FFG are not planning to renew the license in two years or that they may renew the license but only do the 40K rpgs. If they are going to renew the license in two years time and the format of the Star Wars RPG is a success, then I am sure they will redo WFRP along the same lines. The Enemy Within could either be used to sign off V3 or it could be used as an immediate adventure campaign for the new edition. If the format of the Star Wars rpg is not a success then V3 may limp on but I suspect not. Much of it is great but all the extra paraphenalia is not really needed and puts a lot of people off, either through fiddliness or cost. The talent system particularly could do with with a major revamp.