You can always stand firm to what is on paper now, but I wouldn't build a house on that ground, because until its made solid, its questionable.
Then arises the question of what would be considered solid? Rulings are always subject to change at any point in time. Some are more likely to change, if they stand out as BKSS situations.
However, Prime Material Dragon doesn't stand out as a shoddy wording situation to me. I read it very literally, and my interpretation is what I mentioned before. You, however, remember the old scuffles with "a player" (the aforementioned ancient card Ultimate Offering), and almost assume that any card that says "a player" is likely to have an errata slapped on it. "A player" is a valid phrase now, meaning "either/both player(s)", and if they're using it, then that means that's what they want it to mean.
The main task we have as judges is to know how things work, and make sure everyone else does too. Even if it's not working correctly (the BKSS situations, for example), until we hear otherwise we must play the way they say and accept it. Because that's the game.
For the time being, Prime Material Dragon says "a player". So, for the time being, we must play the card assuming it says "a player" (meaning "either/both player(s)"). I'm sure we both do that, masterwoo; in which case the difference is what we expect to happen. I expect there to be no errata (based on trusting that card wording issues have improved in the last 5 years), and you do (based on Ultimate Offering). Either way, for the time being it's irrelevant what we expect to happen.