Blue Ray & HD DVD discs

Does anyone know if Blue Ray and/or HD DVD video discs will play in a standard DVD player? I noticed my local video rental store is offering more and more of these and depending what is out, I may want to rent one of these to get the particular movie or video next on my list.

If they do play, would there by any pluses in video quality or would it be about the same as a standard DVD? I have absolutely no intentions of going to either format in the foreseeable future. Does anyone care to speculate if they believe that eventually DVD's will be available only in these two new formats?
No. They will not play in a standard DVD player.

No, Blu-Ray and HD-DVD will NOT play in a standard DVD player.

I won't hedge bets on format wars anymore, I always seem to back the loser. :(

But there are combo hd-dvd discs out there that play in standard dvd players, you can find a list online of titles.
There are many HD DVD combo disks that will play in HD DVD and in standard DVD players. I have two: Letters from Iwo Jima and 300. They're 2-sided; HD DVD on one side and SD DVD on the other.