Its worth the wait the extra amount! It really is. That 24-105L is VERY capable in so many situations. I've used it for motorsport when up close to the action, ive used it for product and food photography, I use it for the majority of my portrait work, ive used it for landscapes, architectural work, etc... On a 5D, it has a very usable range and rarely do I find myself limited by light. For an extra $250 its a hard bargain to pass up.
And you can open yourself up to so much more shooting than you can with just a 5D and an 85mm. Then again, an 85mm and a 35mm lens would suit you really well.
Have you thought about maybe the 85 1.8 and the Sigma 30mm ?? Its a more capable combo than an 85 and a 50 in my opinion. The 30 or 35 is still good for portraiture as long as you arent in too close. And with an 85 you can still do wasit up.