Genes and memes. It's how things impact the replication of replicators, that will shape future population which even in digital space, consist of units of selection in some way.
I would look to understand community and group cohesion to Durkheim, on religion:
"A religion is a unified system of beliefs and practices relative to
sacred things, that is to say, things set apart and forbidden --
beliefs and practices which unite into one single moral community
called a Church, all those who adhere to them."
This applies to the 'churches' who hold habeus corpus, or free speech sacred too. Challenge what the community enact together the holding sacred of, challenge the communities cohesion. When reproduction is removed, the uses of intimacy and sensory gratification, will be purely cultural, and either help build cohesion, or not. Durkheim juxtaposes social cohesiveness, with anomie.
We discussed how social aims of cooperation, have almost entirely coopted our intuitions towards having sex in private here: How do ethicists tackle the question "Is it immoral to have sex in public places?" Is it possible to use rational and empirical ideas to answer?
and more generally How is Society shaped?
I don't think we are far enough along the track, for this to be much more than an area for science fiction, apart from noting evolutiinary history. Sex emerged very early in evolution, as a way to drive diversity & tune selection of new replicators more dynamically. Without change, with immortal digital entities, there can be only stagnation. It would be inevitable, even with a small fraction of new entities joining from meat-space over time. It's likely a complex set of pressures will act, and at some point something like the Cambrian Explosion.
I'd say the replication of tribal mode-of-living at the scale of the Dunbar Number, could replace an individuals genes as the unit of selection, in digital space. Perhaps with core ideas or narratives or values, generating new groups like religious entrepreneurship & cult-making has in the past.
I look at The 'lying flat' movement in China, and historical Beguine Order to examples of cultural shifts away from a kind of materialism around a family, and pursuing social status in that area.
We imagine we are driven by the qualities of experiences themselves. But in reality what we find pleasurable has been shaped by physical evolution. And what we find fulfilling has been shaped by cultural evolution. If we were robots driven by sensations, everyone exposed to hard drugs presumably would have to become addicted (it's typically less than 15% of users over their lifetime). With the right health & support we can reorientate specific behaviours, from our wider being. I'd say if sex ceases to be important, memory of it will fade. But social purposes may keep it important, especially intense intimacy. And a wider driver of change and recombination will remain essential.
I recommend Hannu Rajaniemi's 'Jean le Flambeur' trilogy for the near-ish future of blurring together real and digital worlds, with deep philosophical thinking from the sobornost to strange-loops.