Microsoft said that they did not want to bring browser to xbox (years ago) because it suked and they couldn’t figure out how to make it work properly (in terms of user experience, etc). I think HWA at least partially solves this issue.
Since IE9 includes hwa and their recent Windows phone platform also utilizes hwa, I think it’s a safe bet.
After all, Xbox 360 already supports HWA for video decoding :)