You don't have a 4K player but you do have a 4K TV?
That's how I did it. Leapfrog back and forth, unless the player's abilities are higher than the set's. I finally got a 4K player and, wow, the differences are huge...
Okay, it is true that going from dual-layer blu-ray to 4K UDH isn't all that bad - the previous release footage looks a tad soft, but still looks reasonably sharp and detailed where it counts the most (compared to upscaled videotape, which is far worse in all aspects...)
But a native 4K UDH disc of the same movie? The new film neg scan at native 4K reveals a lot more detail than I had originally believed, and the accompanying 1080p blu-ray uses the same transfer -- so if nothing else you're still getting a considerable upgrade, with the maximum waiting for when one gets a 4 player.
Not just raw resolution holding image detail, which is amazing enough, the algorithms used for HDR and other aspects simply blew me away. Even tiny set details you would not have seen in previous releases due to lesser resolution, or not in the theater because you're gawking at a 60' screen rather than a condensed 60" one and your eye can't take in all four corners of a 60' screen... that's not a dig, it's actually pretty cool to see, especially when so few examples exist.
Granted, with higher density visuals you'll have to sit a little closer to the TV to really appreciate it all. With lower density visuals (e.g. upscaled videotape), sitting at the same distance will show every bit of compression artifacting so you'll have to sit farther back. Not a big thing... home theater is pretty cool with a 60" screen... Or even with mid-size TVs that, a couple decades ago, were 'theater' (e.g. 40"), as those could be perceived as "drive-in theater but in one's living room and without everyone around you honking their horns or each other's".
Speaking of "UDH", some 4K review sites showed samples of old and new and accidentally reversed them (Star Wars Empire Strikes Back showing 4k as blu-ray and vice-versa... unless they fixed the problems and re-released it, but my disc was just fine. Now if only they'd do the CGI-free versions of the films, or a happy medium between old and new but that's a post for elsewhere...)
But 8K for home video seems rather unlikely for a couple decades, and by then streaming will outperform physical media too...