Managed to get in and see the doctor yesterday and it looks like the ankle injury is just a pulled ligament, so it's just a matter of giving it some time to heal and building back up carefully. That's a big relief as I was a bit worried it would be something more serious. With that said, it is going to make that ankle more prone to injury in the future so I will have to pay more attention to the relevant stretches. He also suggested picking up a brace in the meantime, and a few other measures to help it get better.
Unfortunately, I've now been down for 10 days and I'm not quite ready to head back out at this point so the marathon plans will likely have to be adjusted. I'm now within eight weeks of the race, and Pfitzinger's book suggests that a loss of that much training time should prompt a re-evaluation of readiness. I could likely get back up to the point where I could run it, but with the lost fitness I'm not sure that I'd be able to beat my previous time so it's not really worth the risk of pushing it. I'll likely pick some shorter races this fall (probably the zoo run, and possibly one of the half marathons) and just use this as base training.
The Guelph tri is likely out as well, although one of the HSBC races may still be feasable if I'm cautious about it. Unfortunately the Lakeside race that would have been ideal (Sept 20th) is sold out, so it's either Wasaga (Sept 12th) or moving up to the Sprint Tri (the Try-a-Tri is the only race sold out at Lakeside). Worst case scenario, I could just use the winter to build up my swimming (which is by far my weakest link) and then start out with a sprint tri in the fall.
Either way, it's a load off to know that it wasn't something major and it's just a matter of waiting it out. While it's not really necessary, I'm flirting with the idea of seeing a physiotherapist anyway to see if they have any suggestions on accelerating the recovery process a bit. Having someone with a bit more time to discuss the details of recovering would be helpful - the only downside is that it can get pretty expensive if a few visits are required.
Right now the plan is to work my way back into it. I did 3K in the pool today, and will likely do the same every couple of days for the time being as that will keep my cardiovascular fitness up without stressing out the ankle. Fortunately I still seem to be okay on that front, as I was able to complete two sub-6 minute 400m sets but we'll have to see how that translates to the other sports. Once things start feeling a bit better (hopefully early next week), I'll likely start out with the bike and then re-introduce some slow running into my schedule. Once the pain goes away, I'll then work on bringing myself back up to where I was in a somewhat gradual fashion.