Wait until it gets 6 feet tall and puts out weird seed pods before deciding whether it’s exciting. I’m a little up on grasses at the moment because my corn is sprouting, but some of them really are interesting to watch.
Don’t bet on it. There are plenty of perennial grasses and it’s quite impossible to tell which is which at that stage of growth. If, for example, that’s Sorghum halapense rather than Sorghum vulgare then it could stick around for decades.