The Baikal Miner X10 for example, started with X11/Quark/Qubit Algorythm
Since Release they also added Myriad-Groestl and Skein and they announcend that 2 more will come soon.
For the fact, that they used an ASIC Chip which is "only" designed for X11/Quark/Qubit, they added much more Algos.
I dont think that's impossible to add more algos to the D3, but if Bitmain will do that....
and I believe that is more possible that we all know..
but think about, whoever find a way to mine diff algo will never be an idiot and share it/make it public. why? easy.. profit!
if all D3 users would jump on "new algo" the profit will destroy, no?
so we have to continue life^^ and buy other asics and do/hope the best
hm i dont think so, if all go to another algo, the difficulty of x11 will not rise as fast as before (or it go down, can the diff get down overall?)
but u are are right, life goes on and with my 2 d3's i get some extra money every month so im happy with that

and with the firmware of blissz i hope these 2 have a long lifetime, so thats ok to me