As a 7D user (and 40D before that), I have to agree with the people who've already cautioned against the 24-105. I'm sure it's an excellent lens, but the question is whether it would be a good focal length range for you on APS-C. For years I had a 24-70 2.8 (Sigma in my case) because I thought I'd move to a 35mm sensor camera "one day". I was pretty happy with the IQ (and Canon was too expensive for me), but I just didn't find it a very useful focal length range. I often wanted either wider or longer, so I carried a 10-20 f3.5 and 70-200 f4 as well ... and I found myself using the 24-70 less and less. And I also found myself often using the 10-20 but wishing it was a little bit longer, or using the 24-70 and wishing it could go wider ... or doing a LOT of lens swapping.
Anyway, eventually I bought a second hand 17-55 f2.8 IS and haven't looked back. For travel now, I usually choose one/some/all of 17-55 f2.8, 70-200 f/4 and 28 f1.8 depending on exactly how light I want to travel, what I expect to be shooting and the conditions I expect to be shooting in (wish Canon would make a weather sealed 17-55, or even better would be a weather sealed 15-55+ f2.8 IS!). Btw I was underwhelmed with the 28 f1.8 at first but I have to say it's growing on me.
In your case, I think the first question is whether you'll be happy with the IQ of a super-zoom and can live with the relatively small max aperture. My brother has 18-200 and it's not bad in good light and excluding the ends of its range. If you want better IQ, the 15-85 is worth considering (my sister really likes hers) but there is still the question of whether the max aperture is enough. The 17-55 is obviously an option although the range is less, or perhaps the 15-85 plus something like the 28 f1.8 for the evenings/indoors (and when you want a more compact kit eg wandering around the streets)? Or your Tokina, a 28 f1.8 (or similar, maybe 35 f2?), plus something longer? For something longer, the 55-250 must be worth a considering if you're looking for small and light (I haven't use one so can't really comment). Or there is always the 70-200 f/4 - at least it's smaller than your 2.8!
Of course, so much depends on what you want to shoot / what focal lengths are important to you. If 24-105 covers the focal lengths you want to use, I'm sure you'd be happy with it.
Lastly, the mirrorless idea (OM-D maybe??) has got to be worth thinking about. I'm sticking with my 7D for now (largely because I like to shoot action sometimes) but the size/weight of the mirrorless stuff makes it tempting!
Good luck with whatever you decide!