Yes, but why does Bethesda even owe you DLC? It's completely up to them on what they want to do with their product and whom they want to offer it to. Bethesda doesn't even have to release Dawnguard on PS3 if they didn't want to. They wouldn't even have to make it available to Xbox users. It's their product and with that comes the option to make it available to whom you so choose.
Edited for grammatical errors
no its not the DLC but the fact that we paied just as mutch for our PS3 version and there was no warning on the box or any other indication that you might not get future DLC's or less support.
so PS3 players have just as mutch right to the DLC as xbox360/PC players of the game. in my eyes they do owe us the same as xbox/pc players.
if they didnt whant to owe us anything they should have put a warning on the box and sold the game at a discount.
but because they didnt put any warning on the box or sold the PS3 game at a discount, they do owe us and it would be discrimination not to bring the DLC to PS3 players