Toshiba was invited into the Blu-Ray camp in a bid to end the format war early. Microsoft has always advertised they are providing consumers a choice (ahem....) between a Blu-Ray drive or HD DVD drive for the 360 (at least when consumers have made a clear choice, which is crystal clear now, actually it has been clear for a while considering a 99% Blu-Ray movie sale market share in Japan last year).
Microsoft can adopt Blu-Ray technology like any other company (same terms).