At the end, this will be up to the distributer and out of our hands. However, I doubt any episode will be over 750mb in size (which I think is the larage storage size of the CD) so I see no reason for a DVD (other than a slight installation speed boost).
the optimal size of a cdrom is 750mb but it can be overburned, in some cases to 800mb
but its not recommended
and besides, if the compression used by the installer is good enough they can cram a 3gig game on a cd (extreme case :p)
for me its not a problem if its on a cd or dvd tough