d2h is too having lots of space but they need to procure it. After Anthrix deal scam, ISRO is very much hesitating to poke into more such deal .
ST2 is having huge number of Tps and I am sure d2h would have made a intelligent deal. Unlike Dish TV, d2h require is MPEG4 DVBS2 technology which have an advantage of adding more channels in lesser TP space.
Regarding HD channels, d2h is already heading and will keep adding more and more HD channels. So, it would be a neck-neck competition .
But Tata Sky and ADTV too must have something planned to compete these 2 operators.