I'm barely a PGY1, so feel free to take this with a fairly large grain of salt.** However, I would say that "what are my chances?" depend largely on what you're looking for.
There were multiple programs that didn't fill this year. This included a place like Cincinnati (filled via SOAP), which has an amazing pediatric hospital, great clinical training, and is in the process of building protons. Loved my interview there. I'm not predicting they will or won't fill next year, but they're not a "bottom tier" program by any means. So, if your main goal is to be a rad onc, I think you'll do fine if you apply broadly (though you should definitely do away rotations, especially since you'll need rad onc LORs). If you want to do research at a big name institution, then your lack of honors will hurt you. An extra year of research is most likely not going to give you much of a boost at this point. I wouldn't do it.
If I learned anything on the trail last year, it's that radiation oncology residencies are looking for the complete package (as much as possible). Any single area of deficit can be compensated for in other areas, but more than one starts to really hurt you. The top ranked programs require excellence in all categories. Since you've got an excellent Step 1, strong research credentials, and a name brand school then you're in pretty good shape. Get some strong radiation oncology LORs and you'll be very likely to match. Your (relatively) weaker grades may limit you at the "top 10"-type places, but as you'll find out on the trail this year, there are very few truly bad rad onc residencies. Good luck and enjoy 4th year!
**Just to cover my bases, so you're aware of where my viewpoint is coming from: Step 1 240s, AOA, GHHS, 4 publications (none in rad onc or cancer specifically), bottom tier med school. Matched at a top 20 rad onc program (according to the methodologically
flawed Doximity rankings).