It's a reasonable thing to consider, but it is not an argument against abortion because other as-yet-uncreated fetuses also have valuable futures--maybe even more valuable!--and this fetus may prevent those from ever being created.

So the same reasoning can be used to argue for abortion, indeed, can be used to argue for abortion being a moral obligation, in those cases where current conditions would severely curtail the value of the future of the present fetus, but future fetuses would have markedly better futures which they will only get to inhabit if this fetus does not come to term.

In order to make the argument work, you have to do quite a bit more to separate the anti-abortion implications from the pro-abortion ones. It's not easy: the first few attempts usually tend to fall flat. (For instance, the current fetus exists while the others are just potential...but that isn't very persuasive when people who are fertile and want children have very high reliability of having children.)