That's a shame about Towards the Future, but not unexpected. I wonder if it's a "they're waiting for the international rights to expire"-type thing, or if they're just straight-up not touching those international co-productions outside of Japan? I'd imagine the latter if Mill Creek didn't licence any of them at all.
And wow, Mill Creek really have released a lot haven't they?! Even with all the sets they've put out over the last few years I guess I just assumed they were only about halfway through, given how many Ultraman shows it always seemed like there were.