The long-range computer model forecasts expect that El Niño will continue to strengthen, and indeed they foresee an acceleration to very intense levels in the relatively near future: see below for an example. However, it is interesting to observe that earlier forecasts (e.g. from May, see below) were expecting El Niño to be already considerably stronger than it is now, so the evolution is lagging what was expected. To my mind this is a hint that the episode may peak at lower intensity than is currently predicted and it may be "merely" a strong El Niño rather than a super or record-strength El Niño.
Looking at the bottom rectangle, we see that the strongest La Niña events tend to follow either a significant (but weaker) La Niña event or a moderate to strong El Niño in the previous year. These features of the chart may seem like only sampling variability, but it is generally accepted that La Niña episodes tend to be longer lived than El Niño events. In 115 years of data plotted here, only twice was the ENSO index above +0.75 in two consecutive years, whereas on 8 occasions it was below -0.75 in two consecutive years.