I'm on a very tight budget! I don’t have even have any money for buying the 5D Mark II, at that point I'll sell my 450D...
Ugh, that sounds even worse than me - did you calculate the complete cost, inc. filters and cf cards, maybe flashes, batteries, softboxes, tripods, bags and so on? There are many pros successfully shooting on aps-c, and a standard zoom lens for aps-c like the 15-85 is cheaper than L glass and up to par in iq...
In any case remember that it is very important to have a backup body for many applications, no matter how crappy/outdated it is!
Did not think of Tamron, I'll have a look at that. By the time I buy the 5D Mark II I hope I can pick up a used 24-105mm relatively cheaply!
I don't think the 24-105L will drop any further in used or new/kit price, it's been around for so long. You only could get a rebate for the lens during a Canon promotion or buy it as a kit with the 5d2. Even if a successor would be introduced the price would go *up*, see the 24-70 mk1...