Only the spammiest of spammy SEOs “guarantee” anything.
“Guaranteed” first position rankings, “guaranteed” traffic estimates, and “guaranteed” ROI only live in the deepest, darkest pits of spammy LinkedIn InMails. And only the unsuspecting, naive, plus frankly ignorant businesses fall for these flagrant falsehoods.
But…
That’s not to say you can’t forecast or predict page rankings, traffic estimates, or search ROI.
Nuance and context make all the difference.