4Game

I know lots of us would love to see 'em (and the associated gameplay), but I think it's unlikely they're coming in EDO. Here's why:

They're not coming at launch:

While Odyssey will see players explore a wide range of on and off world locations including station interiors, ship interiors will not be included at launch. (source)

EDO isn't a Seasonal delivery like prior DLCs

Seasons have been dumped:

Firstly on the season plan; I don't think people liked having to pay for multiple updates in one go, so that is something we are going to move away from. (source)

+

We have announced that the ‘season pass’ business model will be superseded by an alternative after the release of 2.4 The Return. (source)

EDO is considered more of an 'all in one' affair:

Going by these snippets from the last few Lavecons anyway…

So this time they're completing the entire mega-update in advance and not telling anyone what's in it until they're absolutely sure about what is going to be delivered. (2018)

The way they told me things, since Horizons was such a, let's stick with the term 'hard lesson', they decided to go with an 'everything at once' approach for the next expansion / update thing. So taking off time to actually work on the thing was necessary but in result as a whole it'll provide a more unified and refined experience that Horizons did not manage.
(2019)

'Station Legs' & 'Ship Legs' were planned to be 2 separate expansions:

Ye Olde Lifetime Pass Roadmap:

We do intend to release small, free updates after launch, but expansions that include significant new features and content will be charged for separately:

• Walking around interiors and combative boarding of other ships
• Combat and other interactions with other players and AIs in the internal areas of star ports

The gameplay outlined for ships interiors + EVA = a lot of dev:

• EVA & external ship repair (source)
• Sneaking in amongst the cargo (source)
• Fighting fires, dealing with toxic spills (source)
• Combative boarding of ships and repelling of boarders.
• Having hull breaches make the internal ship space contiguous with the external space. IE 'Seeing your cargo flying out into space' etc. (source)
• Potentially stealing player ships (source).

TLDR, their objective seems to be to add game tech and mechanics, not just a cosmetic additions etc.

(Whether they achieve any of that is another matter, but it's the type of thing they've floated, and essentially pre-sold with the Lifetime Pass).

Taken in concert, these aspects suggest ship interiors won't be inserted as some form of purely cosmetic add-on. Or arrive as a bonus update to EDO. It's just too much work, not how the DLC system seems to be structured now, and it's all been pre-sold as a stand-alone expansion.