Since you kids are on my lawn anyway...
Blu Ray will not be the final physical format, but all of its successors (including 4K Blu Ray) will be, at best, seriously niche players. Not niche like Laserdisc, niche like SACD. New physical formats require new hardware purchases (let alone new media purchases), and very few will think any difference above Blu Ray will be worth the cost. MAYBE a new format will succeed in the very long term if it's backwards-compatible and cost-competitive with Blu Ray (people would buy 4K players to replace a broken Blu Ray player, but continue to play 2K Blu Rays, in much the same way some people buy Blu Ray players just to play standard DVDs today). Basically I see Blu Ray as a terminal format the same way CDs were. Yes, there were successors but 9 out of 10 people couldn't tell you what they were.
Streaming is already the new rental model, and it may eat into purchases a little bit more than you'd think. Parents used to own stacks of VHS tapes and DVDs that their kids would watch over and over. They bought them so that they wouldn't have to keep renting them, not because they thought they were worth collecting. Now if you have a Netflix subscription you can watch Thomas & Friends once a week for five years, and then, mercifully, you can stop. People will still purchase Blu Rays (and DVDs), but not like they used to--only for the things they really, truly love. I really, really don't see how purchased-streaming plans like UltraViolet make any sense in a world where people already have Netflix-like subscriptions for rental-type streams. If you already have the subscription and you want to stream it, just save the cash and stream it from Netflix. Who cares if you don't own it?
I think there's already a consumer fatigue with revisionism and gimmickry related to media upgrades, which will dampen any enthusiasm for a new format. Not everyone is as worked up about Star Wars as we are, but really, let's say you actually own and like the Blu Rays--are you really going to upgrade to 4K just so you can watch Alderaan shoot first, or watch it in 3D, or with pre-rendered interpolated frames for a 48fps presentation? What about other films--a few more deleted scenes, a different shade of teal & orange? Nobody cares. I can find lots of faults with most modern Blu Rays, but most of them could be fixed without changing the Blu Ray format itself (better transfers, less compression, less DNR, etc). More resolution and the things that would require a new format may help, but they're not even in the first 10 pages of improvements I'd typically like to see.
Of course I suppose I should mention I have a history of being a complete Luddite and missing many very important trends. I didn't see much point in cell phones until they started removing pay phones, for example. So there you have it.