Unfortunately I'm afraid some fragmentation is going to happen, though not necessarily around browser axis.
This is actually a deeper problem. It's not about standards, it's about performance.
"Old" web (where old is almost anything up to just recently) got to the point that whatever you do, can run reasonably well virtually everywhere (welcome to dream, write once, run on PC / Mac / Linux / iPhone / Android).
"New" web (what runs on nightlies / alphas / canaries) will need enough raw power for all its shininess.
Old web was seriously underusing resources on modern computers, so there was enough slack to cut / optimize away. New web is about reclaiming back this idle unused power.
If you get a terrible performance in some recent demos (and yet you see other people telling how good something runs), welcome to inequalities of new HW accelerated web.
Problems can be:
a) bad GPU drivers preventing your HW performing well (old drivers, weird manufacturer's driver versions for notebooks, not-completely-fine-tuned drivers for Linux / Mac),
b) your HW is not very powerful (netbooks, mobile devices, integrated GPUs).
This is something standards can't hide. You can have software emulation fallbacks to be compliant, but this will not really help practically, especially not on underpowered devices.
And this is in addition to performance differences coming from different browsers implementations (which may all perfectly comply with standards).