It didn't mean anything in my case. My maternal grandfather had a full head of white hair by the time he died in his late 70s. However, my maternal grandmother had baldness on both sides — bald father (though I can't say what kind or to what degree since he died when my mother was a child), and her mother's sister had no hair on her scalp when she died at 90-something — though interestingly enough, my grandmother herself maintained a reasonably thick head of hair all her life. My mother's brother has been shaving his head since he was in my age range (late 20s early 30s, he's in his 50s now), and he's disclosed that his hair still grows on top, but very thin, probably like mine will end up. My father is almost 60 with minimal loss and wears his hair roughly shoulder-length.
The X chromosome is said to contain a gene for an androgen reception which increases the odds of male pattern baldness if one possesses a particular allele (copy) of that gene. A male could only inherit it from his mother, while a female can inherit it from both parents, so you would just as likely inherit your grandmother's version of it as your grandfather's. Even then, that defective androgen receptor is not enough; there are plenty of other, autosomal genes that contribute to male pattern baldness. And then you factor in mutations, genes reacting to each other in unpredictable ways, genes activating or not activating by sheer luck of the draw, etc. So yeah, your mother's father's hair, or really any guy in your family, could reflect your risk factor of experiencing baldness, but it is far from a sure thing.