Personally, I could see the future of visitor-animal interactions in US zoos going in either direction. On one hand, you are absolutely correct that they are very popular with visitors. The fact it lets guests feel connected to animals is also a great point- and one that is integral to the direction many zoo education departments have been trending in recent years, with more of a focus on empathy training and profound experiences. In those regards, it seems very likely that visitor-animal interactions, whether they be walk-throughs, touch tanks, or animal ambassador experiences, could become more common in the future. I'd even throw into this the fact many zoos have started bringing in bird shows during the summer- as even though there isn't direct visitor-animal contact, it does fit into the idea of close-up, profound experiences with animals and building closer connections with the animals.
That said, any visitor-animal interaction in zoos is going to be inherently more risky than a traditional exhibit. This isn't to say they are high risk (many of the common ones, such as walk-through aviaries and goat feeding, are fairly low risk), but some zoos are always going to be more risk-averse than others, for whatever reason. It's easy to see how some incident or event could spur the reduction of certain existing visitor-animal interactions. While so far I'm not aware of any incidents in kangaroo walk-throughs, kangaroos are potentially dangerous animals. Would all it take be one incident at a single zoo for other zoos to re-think having kangaroo walk-throughs? Likewise, there have been recent cases where multiple zoos have lost all of their stingrays in a touch tank. Other zoos and aquariums may look at these cases as a reason not to add a stingray touch tank to their collection.
Perhaps the biggest risk in walk-throughs is disease, and we are living in a time with increasing zoonotic disease concerns. Walk-through aviaries were one rather high-risk exhibit during the height of Avian influenza- and Toronto Zoo actually transformed each of their walk-through aviaries into a non-walk-through as a reaction to the risk of Avian flu. Is that an appropriate response or overreaction? Not my place to judge, but it goes back to the fact some zoos would be more risk averse than others. During the aftermath of COVID-19, visitor-animal interactions remained a concern of many zoos, in trying to keep their collection safe from the virus. It's easy to see how certain zoos may have either closed visitor-animal interactions or removed high-risk species as a result of the pandemic. I'm not here to judge whether zoos made the right changes and precautions or not, merely am pointing out potential factors influencing the future of visitor-animal interactions in zoos.
Outside of the risks of visitor-animal interactions, animal welfare is another area that could influence the future trends. With good zoos putting more of an emphasis on welfare (and rightfully so!), it is possible that some or all zoos re-evaluate their interactive exhibits from a welfare perspective. This is already being done at some zoos in regards to animal ambassador programs. While I don't know of any zoos eliminating their ambassador program, many zoos are putting more of an emphasis on ensuring choice and control on the part of the animal, and some zoos are also re-considering having touch opportunities with ambassadors. While I don't know if there are any welfare concerns with walk-through exhibits, I can easily see how new research could change that. Imagine a study being done evaluating the cortisol levels (stress hormone) and behavior of kangaroos when there is and is not visitors in their walk-through exhibit. I have no clue what results such a study would find, but could a study of that nature cause zoos to reconsider kangaroo walk-throughs? That I'm not sure of.
Overall, one trend I do expect is for more and more visitor-animal interactions to be monitored by staff. I suspect more zoos in the future will have staff present in walk-through aviaries to ensure guests are following the rules and respecting the animals, as well as providing educational information. Most touch opportunities, and many walk-throughs, are already monitored, and I suspect a greater proportion of them will be in the future as this is a great way to mitigate some of the risks and concerns surrounding visitor-animal interactions that I have laid out.
