i think eggy missed the point.
The "long beam" is ONLY in the original metroid, its quite useless really, and pointless. In the original metroid, her beam only shot about 1/2 way across the screen, the long beam made it shoot all the way.
in metroid 2, 3, 4 and prime, she didn't get this upgrade, because its... a very, very stupid upgrade.
If it came before the first metroid, getting the long beam would also make sense.
But, im pretty sure Zebes wouldn't. I'm 99.9% sure that Samus' first time on zebes was the original metroid. (as it was also her first time encountering a metroid, which is why a prequel couldn't have any metroids in it.)
I'm 99.9% sure its a remake, though, as i mentioned, a HEAVILY EXPANDED remake, At least there will be alot of metroids in this game if it is. every game since metroid 2 was lacking metroids, or made them seem horribly weak. (hell, even the omega metroid at the end of metroid 4 was pathetic compared to the suckers in metroid 2)