No, the meat would not be forbidden if the blessing was skipped, in most cases. The blessing need not be repeated if it was skipped.
See Simla Chadasha (19:1), who writes:
ואי לית ליה לא יברך אחר השחיטה אפילו תוך כדי דיבור דכיון דראוי היה
לברך קודם ודחי נפשיה הואיל ואדחי אדחי אבל השחיטה כשרה אפילו לעצמו
ואפילו הזיד ולא בירך ומ״מ אם רואים שהעם פרוצים ומקילים בברכות יש לקנוס
המזיד ולאסור אותה שחיטה לו ולהלקותו אבל אחרים מותרים
If the blessing was not made, do not make the
blessing after the shechita, even "תוך כדי דיבור" (see this
answer for some detail on תוך כדי דיבור), since the blessing is
missing, it's over. The שחיטה is valid, in any event -- even for the
slaughterer himself, even if he skipped the blessing on purpose.
However, if we see that there are many people who are skipping this
blessing on purpose, then we will punish someone who skips the blessing
on purpose -- we will forbid the meat from that shechita to him, and
give him lashes; however, the meat is still allowed to others.
( my translation )
It should be noted that the Mordechai in the beginning of Chullin quotes Eldad Hadani as saying that meat slaughtered without a bracha is "פיגול" (likely a stand-in word for "אסור," similar to "טריף" in our vernacular), though the Mordechai says that it is "חומרא ולא נהגינן כוותיה," a stringency that we do not hold ourselves to. (see also this answer for another rejected ruling of Eldad Hadani)