Yes, it’s possible you stay friends and never anything more. Twin flames don’t always end up together in this lifetime, at least. For some, friendship might be as close as you get. Although I do agree with others here, wehther that is real or healthy friendship might be up for debate.
For most of us, friendship during separation usually keeps both people stuck. The intensity overrides whatever conscious labels you put on it. You watch them with other people and it kills you because the feelings are romantic, not platonic. Acting normal back when you want to scream isn’t friendship - it’s just suppression.
Most people who successfully maintain friendship report “years of daily crying” before they could genuinely accept the loss of romantic possibility. That’s not an exaggeration. The grief has to be processed fully before friendship becomes anything other than torture. The real question isn’t can you be friends. It’s can you genuinely accept a platonic relationship without suffering, without hope, without watching them with others and feeling like you’re dying inside.