Duathlon Central has published a list of duathlon events for 2018, and though they cover two of the three Ontario multisport series (MSC and Subaru), for some reason (southern Ontario bias?) they don't give the Somersault series any coverage.
So, here is what I've been able to come up with for the eastern Ontario duathlon schedule for 2018.
The CMC Duathlons are pretty low key from what I understand, and they haven't established dates for those yet, I'm just guessing at when they'll run them based on previous years. Everything else is official.
An interesting mix of distances available. The usual sprint (2.5/20/5) and standard (5/40/10) distances, plus quite a few sprints with a 30K bike, which should appeal to strong cyclists. My threshold for "eastern Ontario" is races that I would reasonable drive to the morning of... hence my inclusion of the technically-in-Quebec Gatineau race (30 minute drive for me) but not, for example, the Overdrive races (about 3.5 hours).
I don't think any other races will materialize, unless some previously tri-only races offer duathlons, so this is likely what's on offer for 2018. I've got a good idea of which races I'll plan on, but as per usual we'll see where my fitness is and what life dishes out.