LogFAQs > #980040031

It's very obvious to me that it's being saved for the Switch's successor, which likely happened because of the restarted development, and not wanting to force a long-distanced-from-the-series Retro Studios to have to work on (as) underpowered hardware (which wouldn't surprise me if that was at least part of the reason why the development got restarted in the first place)

I'll definitely still play it, but I'm not super eager/hyped over it, so it doesn't matter to me how long it's been taking. Prime was clearly originally intended to just be a trilogy with the 3rd game having a sense of finality (aside from that one little 100% completion post-credits stinger scene which it wouldn't even surprise me if it ends up not even being a plot point in Prime 4), so frankly Prime 4 just comes off to me as a sort of extra/DLC content overall rather than some long-awaited proper continuation to an unfinished story.