I broke my big toe on a trail run during my freshman year of college soon before the indoor track tryout for walk-ons (and took me out of that race). Biking would help with keeping your aerobic strength up a bit, but you'd have to do a lot of biking to get that benefit. I tried aqua jogging and found it really difficult to tell if I was maintaining anything or not - in retrospect I probably wouldn't have even done that because I found it so difficult to tell if it helped.
You could try swimming too of course, but if I could go back (or recommend to you) I'd say just consider yourself a cyclist until you can run again. Love the bike, let your mind recover running-wise until you can run again. Aqua jogging took a bit out of me mentally because I had to work so hard in the pool yet still couldn't tell if it was really helping much. Sure it probably did a little, but for all the work I did in the pool I don't think it was worth it.