Sounds perfectly fine to me. At that age DS was still on 8-10 They're all different and they know best what they need.
How do you feel about it? Sounds like you're ok with 5 feeds - if so, no need to change anything. He'll gradually take less milk as he eats more solids - exactly when this switch happens varies a great deal between different kids, but they do it when they're ready to. By 15 months my DS was only having 3-4 feeds (big difference!) and that's when he really started eating a lot.
I wouldn't use soy formula because of the issues associated with soy milk. Toddler milk is really unnecessary, and it's fulll of sugar. If you want to give him something else, at this age you could try a little bit of cow's milk and see (if you haven't tried him on dairy already). If he's getting other sources of calcium you don't really need to worry about giving him other milk at all.