I honestly can't see what design goal that would be and why it would be a hardware problem that a game must be 30fps. Physics, A.I, world size, etc, in game development it has always been about simplifying things until the engine can handle it, hopefully in a clever enough way that it won't be noticeable by the gamer.
Cross-platform multiplayer in a game made for PC which is then downported to console is the only situation where I guess a weak hardware could be the main problem for a low framerate. If the devs can't simplify A.I, physics, etc without the gamer noticing a difference between the platforms they may be forced to run the game slower on console to not break the game.
But in those situations they wouldn't make it cross-platform if the framerate was important, they would run multiplayer on PC and console separately and simplify things on console to make it run at 60fps on console too, which in the end yet again is a dev decision rather than a hardware problem.
The truth is that there is always a way to run a game at 60fps no matter what game or genre it is on every single hardware that is able to output new images at 60hz from the display port.
We've had both 60fps and 30fps games on NES/C64/etc and we still have it on Pro and will have it on XBX and PS5 and XB2 etc too. Lets check again in 10 years and I can guaratee that it'll be exactly the same. If we're lucky there will be more 60fps then, but it won't have anything to do with the hardware but rather a general change among devs that 60fps should be the target to aim for.