The thing is, I think walking around should be PART of the core game. It's not a novelty.
Boarding, stealing ships, EVA to investigate wreckages, doing passenger transport with the Beluga Liner or the Orca, talking to NPCs, having multiple crew on your huge ship manning turrets and stuff... None of this can be considered a "novelty" since it DRASTICALLY changes the game.
That's why I personally think it's better to add it sooner rather than later since it will introduce so many new mechanics and ways to play the game that it will have a gigantic impact on the game as it is now and will basically break everything. the earlier they do this, the easier it will be to fix the game and balance things up again after the addition of spacelegs. The more polish you add to a game, the harder it is to start implementing big features.
The way they would do it it would be a novelty. Look at how they've handled literally everything else. We're better off without the type of space legs/FPS that FDev is likely to be able to create. We don't need more empty dead environments with no dynamism, variation, persistence, unique art assets, or interactivity. We don't need any more single-purpose shallow game mechanics. It's time to add depth to the core experience. Let's do gas giants. Let's do in-depth hyperspace jump mechanics. Let's do interesting uses for surface scanners. Let's do "tier 2" NPCs and the ability to communicate with NPC ships. Let's populate planet surfaces with NPC SRVs, Conflict Zones, mining sites. Let's have ship names and ship reputations. Let's have different systems with different laws and different types of appearances and behaviors that actually matter. Let's have a trading system where price fluctuations and the BGS actually matter. Let's get rid of combat logging. Let's NEVER hear the words "3D Printing" used as an explanation for a hokey and unconvincing game mechanic, Etc.