In this case the browser market share doesn't mean much.  It is mindshare among the people providing the videos that matters.  The way this particular battle is going to play out is that Mozilla will stick to its guns for a while and will continue to lose marketshare to Chrome, video providers will encode in HTML5/h.264 and Flash and eventually Firefox users on video sites will start seeing messages similar to the ones IE6 users see on some sites.  The wildcard in this is Microsoft.  If someone over there develops a clue they will jump on the h.264 bandwagon just to hose Mozilla -- IE8 will stop bleeding marketshare and this will provoke the video providers to move hard and fast to HTML5/h.264, forcing MozillaCorp to eat the costs of buying h.264 licenses and sticking a sharp stick in Adobe's eye as icing on the cake.