Seeing as they (they being the Blu Ray collective, not just Sony) would make money from it, I doubt they'd deny Microsoft if it came to that. They might if they wanted to damage Microsoft, but it wouldn't be hard for Microsoft to just use a different format. Proprietary media isn't exactly uncommon in consoles. They could even use HD-DVD even if it isn't the standard. In fact, it wouldn't suprise me if Microsoft and Nintendo were to snub Blu Ray and opt for HD-DVD or some other format in their next consoles.
I know you believe you understand what you think I said but I don't think you realize that what you heard is not what I meant.