The problem with cramming more pixels onto any sensor isn't just their size, its the electronic 'noise' that they generate - this is what causes the sensor artifacts (seen as odd pixels of bright colours) especially at higher ISO levels.
Whilst Canon may - may - introduce a 5D replacement with a higher megapixel sensor, you've got to consider that the 'best' Canon DSLR - the EOS 1DS MkII - currently has a 16MP sensor. This model may be upgraded (its been around since 2004) to a higher megapixel sensor, but if Canon put, say a 22mp sensor in the 1DS MkIII (or whatever they call it!) for pure marketing reasons, I can't see them also putting a 22mp sensor in the 5D's "replacement".
The images taken from a 5D, especially when paired with 'L' glass are - with a competant photographer - good enough for commercial work. I know several "pros" who use the 5D as their main camera (mainly wedding/portrait types).
If you really want a 22mp camera, then the bank job (and a 1DS MkIII - or whatever its called) might be your best bet. Remember with the 30D, Canon retained the sensor from its predecessor; there's nothing 'wrong' with the 5D sensor!
What might be a good idea for you (and this is a tip I've used myself, when considering the purchase of a 30D); take one of your own compact flash cards to a camera shop, ask them if you can have a play with a 5D/24-105, and fire off a few frames - in the shop, or wherever, doesn't matter, as long as you get a good exposure.
Then, take "your" card, and get the images (post-processed in Photoshop, if you have it) printed at A2 and/or A3 size by a commercial printer - this will only cost a few quid - and then that will give you a better idea if the 5D will be suitable for the kind of photography and size of prints you want? (Of course, you may then end up buying an A2 printer!)