So a booster every 3 months at that rate. 3-4x a year sounds more realistic.
Not necessarily. This waning is for infection only, protection against severe disease is still actually increasing at this point for boosters.
Delta and omicron are different beasts when is comes to immune escape - its not a surprise that omicron will get around protection against infection even with a booster, maybe a surprise it’s noticeable already. But it does have very high immune escape.
The key is protection against severe disease, reduction of this was what drove the push for boosters. This could still remain very high after the booster dose, or drop eventually only in particular older or vulnerable groups. For groups where it remains high, a 4th shot isn’t required. Remember the aim is to bring down severe disease, not prevent every infection if those infections don’t require treatment or lead to bad outcomes.