No worries, reading between the lines of my initial post you may have picked up I've had run ins before with so called experts which tend to get my back up
First up, and please don't take this the wrong way, with the matter in hand when speaking to your expert or others please be specific; there is a difference between talking about "HTML" and "HTML5". In my experience "experts" try to score points on any small ambiguities.
HTML has been around for around 25 years, the numbers after it (e.g. HTML5) basically indicate standards the version complies with. Although people had been using components of HTML5 for a few years prior, between HTML4 and the new standard HTML5 being recommended by W3C was a 15 year gap. The standards for HTML5 where only finalised in 2014 so whenever the next version will be standardised is anyone's guess but I'd wager on it being years rather than months.
A Google search will bring up plenty of hits stating HTML5 is the future; not many (if any) will say you're wrong to use it.
To reiterate, Moodle is basically irrelevant to your issue. What you develop in Captivate is platform agnostic, to not publish a cross-platform learning object (which is where your reference to HTML5 comes in) from Captivate at this time based on doubts re "the longevity of HTML5" is illogical IMHO. If, and that is a ridiculous "if", HTML5 died tomorrow, simply open the project in Captivate and republish to another option; there's plenty of them (see here for example).
I really would love to hear what alternatives this expert is putting forward, as I said in the original reply I'm not endorsing Captivate (it's just one tool of many) but I don't see what the issue with HTML5 could possibly be. Sounds to me his/her issue is using Captivate more than anything else.