a few points...
first of all its very wrong to label MD as a failed format. Its killed off DCC and has a pretty strong presence nowadays. Of course, you'd have to be mad to buy pre recorded MDs but as a recording format, it wipes the floor with normal audio tape and is certainly worth getting.
Re blue laser DVD.
Compatibility - will a second laser be required? Maybe you can use a different lens to focus blue lasers onto infra red for DVD - if so (or if its cost efficient to have a second laser) then yes, it would be mad to release a blue laser deck without standard DVD compatibility.
Personally this could be the holy grail for standard definition TV, offering high recording capacity at the highest standard DVD bit rate. Present standard DVD recorders fail miserably.
But - will they bother with non Hi-Def territories - why confuse the market by having another DVD standard. Certainly I couldnt see any software manufacturers using blue laser technology for 625 line material - you'd need to release two types of disc or have expensive to manufacture hybrid discs in order to release material.
Also - notice that the discs are in caddies - if this is going to be the case for all blue laser discs, then how would you even play a hybrid disc on a standard player?
In short, for the UK and other standard definition territories, I dont think this is anything to get immediately excited or worried about. Blue laser DVD has been in the offing for the last 5 years and I suspect it will be another 3-5 before useful and more importantly commercial applications are found for it outside the realm of Hidef where a completely new platform could be created.