Depends on what you mean by "icon"
The Icons were largely in-house IPs developed before HHN was the juggernaut it is today
They appeared on all print and ad material, had in park presence, and normally their own house (or made a guest appearance in one)...at least the major 4
If we use Weeknd as an example, he was on all print and ad material, had in park presence, and his own house..He's clearly the biggest IP and could be argued as the most iconic part of this year's event..is he an icon? Well, depends on how you define it.
If you're talking making a character like Chucky "the" event IP/icon, that would be counter to Universal's approach as just one IP would probably be considered not good enough by the higher ups
Yet, I could certainly see them doing something creative in the streets like they did with Pumpkin Lord, or even the Terra Queen, where they are "in park" icons but just not present on ads or in a specific house.
Chucky, for instance, taking over HHN would be kind of interesting I guess..Kind of like "Chucky presents: HHN32" or something...but there would need to be more IP surrounding him
In that case it's like one tiny step away from what they're already kind of doing with IP and may be confusing to some
Again, the function of the Icons was to provide a host or face to the event in an IP-less(ish) era and enforce the branding of that year...The function of the IPs is to provide a hook to entice people to come and HHN is the overall brand now...where as before it wasn't big enough to do so
It's interesting that things have circled back around
The first years of HHN used IP to "introduce itself"...and the function was relatively the same as it is now..its come full circle..although the HHN brand is much stronger